Vaccine effectiveness of heterologous CoronaVac plus BNT162b2 in Brazil

Effectiveness of different booster vaccine combinations against SARS-CoV-2 during a six-month follow-up in Mexico and Argentina

Introduction

Given the limited number of patients in Latin America who have received a booster dose against the COVID-19, it remains crucial to comprehend the effectiveness of different vaccine combinations as boosters in real-world scenarios. This study aimed to assess the real-life efficacy of seven different vaccine schemes against COVID-19, including BNT162b2, ChAdOx1-S, Gam-COVID-Vac, and CoronaVac as primary schemes with either BNT162b2 or ChAdOx1-S as booster vaccines.

Methods

In this multicentric longitudinal observational study, participants from Mexico and Argentina were followed for infection and SARS-CoV-2 Spike 1-2 IgG antibodies during their primary vaccination course and for 185 days after the booster dose.

Results

A total of 491 patients were included, and the booster dose led to an overall increase in the humoral response for all groups. Patients who received BNT162b2 exhibited the highest antibody levels after the third dose, while those with primary Gam-COVID-Vac maintained a higher level of antibodies after six months. Infection both before vaccination and after the booster dose, and Gam-COVIDVac + BNT162b2 combination correlated with higher antibody titers.

Discussion

The sole predictor of infection in the six-month follow-up was a prior COVID-19 infection before the vaccination scheme, which decreased the risk of infection, and all booster vaccine combinations conveyed the same amount of protection.

Risk factors for SARS-CoV-2 infection at a UK electricity-generating company: a test-negative design case-control study

OBJECTIVES

Identify workplace risk factors for SARS-CoV-2 infection, using data collected by a UK electricity-generating company.

METHODS

Using a test-negative design case-control study, we estimated the OR of infection by job category, site, test reason, sex, vaccination status, vulnerability, site outage and site COVID-19 weekly risk rating, adjusting for age, test date and test type.

RESULTS

From an original 80 077 COVID-19 tests, there were 70 646 included in the final analysis. Most exclusions were due to being visitor tests (5030) or tests after an individual first tested positive (2968).Women were less likely to test positive than men (OR=0.71; 95% CI 0.58 to 0.86). Test reason was strongly associated with positivity and although not a cause of infection itself, due to differing test regimes by area, it was a strong confounder for other variables. Compared with routine tests, tests due to symptoms were highest risk (94.99; 78.29 to 115.24), followed by close contact (16.73; 13.80 to 20.29) and broader-defined work contact 2.66 (1.99 to 3.56). After adjustment, we found little difference in risk by job category, but some differences by site with three sites showing substantially lower risks, and one site showing higher risks in the final model.

CONCLUSIONS

In general, infection risk was not associated with job category. Vulnerable individuals were at slightly lower risk, tests during outages were higher risk, vaccination showed no evidence of an effect on testing positive, and site COVID-19 risk rating did not show an ordered trend in positivity rates.

Immunogenicity of COVID-19 adsorbed inactivated vaccine (CoronaVac) and additional doses of mRNA BNT162b2 vaccine in immunocompromised adults compared with immunocompetent persons

Inactivated COVID-19 vaccines data in immunocompromised individuals are scarce. This trial assessed the immunogenicity of two CoronaVac doses and additional BNT162b2 mRNA vaccine doses in immunocompromised (IC) and immunocompetent (H) individuals. Adults with solid organ transplant (SOT), hematopoietic stem cell transplant, cancer, inborn immunity errors or rheumatic diseases were included in the IC group. Immunocompetent adults were used as control group for comparison. Participants received two CoronaVac doses within a 28-day interval. IC received two additional BNT162b2 doses and H received a third BNT162b2 dose (booster). Blood samples were collected at baseline, 28 days after each dose, pre-booster and at the trial end. We used three serological tests to detect antibodies to SARS-CoV-2 nucleocapsid (N), trimeric spike (S), and receptor binding domain (RBD). Outcomes included seroconversion rates (SCR), geometric mean titers (GMT) and GMT ratio (GMTR). A total of 241 IC and 100 H adults participated in the study. After two CoronaVac doses, IC had lower SCR than H: anti-N, 33.3% vs 79%; anti-S, 33.8% vs 86%, and anti-RBD, 48.5% vs 85%, respectively. IC also showed lower GMT than H: anti-N, 2.3 vs 15.1; anti-S, 58.8 vs 213.2 BAU/mL; and anti-RBD, 22.4 vs 168.0 U/mL, respectively. After the 3rd and 4th BNT162b2 doses, IC had significant anti-S and anti-RBD seroconversion, but still lower than H after the 3rd dose. After boosting, GMT increased in IC, but remained lower than in the H group. CoronaVac two-dose schedule immunogenicity was lower in IC than in H. BNT162b2 heterologous booster enhanced immune response in both groups.

How has research on the effectiveness and safety of COVID-19 vaccination been evaluated: a scope review with emphasis on CoronaVac

Introduction

The control of the COVID-19 epidemic has been focused on the development of vaccines against SARS-CoV-2. All developed vaccines have reported safety and efficacy results in preventing infection and its consequences, although the quality of evidence varies depending on the vaccine considered. Different methodological designs have been used for their evaluation, which can influence our understanding of the effects of these interventions. CoronaVac is an inactivated vaccine, and it has been assessed in various studies, including clinical trials and observational studies. Given these differences, our objective was to explore the published information to answer the question: how has the efficacy/effectiveness and safety of CoronaVac been evaluated in different studies? This is to identify potential gaps and challenges to be addressed in understanding its effect.

Methods

A scoping review was carried out following the methodology proposed by the Joanna Briggs Institute, which included studies carried out in humans as of 2020, corresponding to systematic reviews, clinical trials, analytical or descriptive observational studies, in which the effectiveness and/or safety of vaccines for COVID19 were evaluated or described. There were no age restrictions for the study participants.

Results

The efficacy/effectiveness and safety of this vaccine was assessed through 113 studies. Nineteen corresponded to experimental studies, 7 of Phase II, 5 of Phase IV, and 4 were clinical trials with random assignment. Although some clinical trials with random assignment have been carried out, these have limitations in terms of feasibility, follow-up times, and with this, the possibility of evaluating safety outcomes that occur with low frequencies. Not all studies have used homogeneous methods of analysis. Both the prevention of infection, and the prevention of outcomes such as hospitalization or death, have been valued through similar outcomes, but some through multivariate analysis of dependencies, and others through analysis that try to infer causally through different control methods of confounding.

Conclusion

Published information on the evaluation of the efficacy/effectiveness and safety of the CoronaVac is abundant. However, there are differences in terms of vaccine application schedules, population definition, outcomes evaluated, follow-up times, and safety assessment, as well as non-standardization in the reporting of results, which may hinder the generalizability of the findings. It is important to generate meetings and consensus strategies for the methods and reporting of this type of studies, which will allow to reduce the heterogeneity in their presentation and a better understanding of the effect of these vaccines.

Dynamic clade transitions and the influence of vaccine rollout on the spatiotemporal circulation of SARS-CoV-2 variants in São Paulo, Brazil

Since 2021, the emergence of variants of concern (VOC) has led Brazil to experience record numbers of in COVID-19 cases and deaths. The expanded spread of the SARS-CoV-2 combined with a low vaccination rate has contributed to the emergence of new mutations that may enhance viral fitness, leading to the persistence of the disease. Due to limitations in the real-time genomic monitoring of new variants in some Brazilian states, we aimed to investigate whether genomic surveillance, coupled with epidemiological data and SARS-CoV-2 variants spatiotemporal spread in a smaller region, can reflect the pandemic progression at a national level. Our findings revealed three SARS-CoV-2 variant replacements from 2021 to early 2022, corresponding to the introduction and increase in the frequency of Gamma, Delta, and Omicron variants, as indicated by peaks of the Effective Reproductive Number (Reff). These distinct clade replacements triggered two waves of COVID-19 cases, influenced by the increasing vaccine uptake over time. Our results indicated that the effectiveness of vaccination in preventing new cases during the Delta and Omicron circulations was six and eleven times higher, respectively, than during the period when Gamma was predominant, and it was highly efficient in reducing the number of deaths. Furthermore, we demonstrated that genomic monitoring at a local level can reflect the national trends in the spread and evolution of SARS-CoV-2.

Immunogenicity and durability against Omicron BA.1, BA.2 and BA.4/5 variants at 3-4 months after a heterologous COVID-19 booster vaccine in healthy adults with a two-doses CoronaVac vaccination

Background

Several countries have authorized a booster vaccine campaign to combat the spread of COVID-19. Data on persistence of booster vaccine-induced immunity against new Omicron subvariants are still limited. Therefore, our study aimed to determine the serological immune response of COVID-19 booster after CoronaVac-priming.

Methods

A total of 187 CoronaVac-primed participants were enrolled and received an inactivated (BBIBP), viral vector (AZD1222) or mRNA vaccine (full-/half-dose BNT162B2, full-/half-dose mRNA-1273) as a booster dose. The persistence of humoral immunity both binding and neutralizing antibodies against wild-type and Omicron was determined on day 90-120 after booster.

Results

A waning of total RBD immunoglobulin (Ig) levels, anti-RBD IgG, and neutralizing antibodies against Omicron BA.1, BA.2, and BA.4/5 variants was observed 90-120 days after booster vaccination. Participants who received mRNA-1273 had the highest persistence of the immunogenicity response, followed by BNT162b2, AZD1222, and BBIBP-CorV. The responses between full and half doses of mRNA-1273 were comparable. The percentage reduction of binding antibody ranged from 50 % to 75 % among all booster vaccine.

Conclusions

The antibody response substantially waned after 90-120 days post-booster dose. The heterologous mRNA and the viral vector booster demonstrated higher detectable rate of humoral immune responses against the Omicron variant compared to the inactivated BBIBP booster. Nevertheless, an additional fourth dose is recommended to maintain immune response against infection.

Evidence synthesis and pooled analysis of vaccine effectiveness for COVID-19 mRNA vaccine BNT162b2 as a heterologous booster after inactivated SARS-CoV-2 virus vaccines

Introduction of primary COVID-19 vaccination has helped reduce severe disease and death caused by SARS-CoV-2 infection. Understanding the protection conferred by heterologous booster regimens informs alternative vaccination strategies that enable programmatic resilience and can catalyze vaccine confidence and coverage. Inactivated SARS-CoV-2 vaccines are among the most widely used vaccines worldwide. This review synthesizes the available evidence identified as of May 26, 2022, on the safety, immunogenicity, and effectiveness of a heterologous BNT162b2 (Pfizer-BioNTech) mRNA vaccine booster dose after an inactivated SARS-CoV-2 vaccine primary series, to help protect against COVID-19. Evidence showed that the heterologous BNT16b2 mRNA vaccine booster enhances immunogenicity and improves vaccine effectiveness against COVID-19, and no new safety concerns were identified with heterologous inactivated primary series with mRNA booster combinations.

Half dose ChAdOx1 nCoV-19 vaccine was equivalent to full doses to reduce moderate and severe COVID-19 cases

Objectives

Previously, we presented the effectiveness of ChAdOx1 nCoV-19 half-dose (HD) immunization for preventing new COVID-19 cases. Here, we evaluated the administration of an HD of ChAdOx1 nCoV-19 in the primary immunization protocol (up to two doses) in reducing moderate and severe cases, hospitalizations, and deaths when compared to the administration of full doses (FD) after a long-term follow-up.

Methods

We evaluated data from 29,469 participants between January 2021 and November 2022 who received an HD or FD vaccine and crossed this information with their medical records to identify those who developed moderate or severe cases. All participants were classified into four groups according to their immunization status and followed 500 days after the last vaccine administration.

Results

The propensity-score matching analysis indicates that the administration of the two HDs of ChAdOx1 nCoV-19 was equivalent to the use of two FDs to reduce moderate and severe COVID-19 cases. The relative risk of being infected and developing moderate or severe conditions after the administration of at least one HD or FD was similar 150 or 500 days after the administration of the immunizers.

Conclusion

Administering two HDs can be used safely as a cost-effective alternative to the primary immunization protocol.

Vaccination status of COVID-19 patients followed up in the ICU in a country with heterologous vaccination policy: A multicenter national study in Turkey

OBJECTIVE

Vaccination against severe acute respiratory syndrome coronavirus-2 (SARS-2) prevents the development of serious diseases has been shown in many studies. However, the effect of vaccination on outcomes in COVID-19 patients requiring intensive care is not clear.

METHODS

This is a retrospective multicenter study conducted in 17 intensive care unit (ICU) in Turkey between January 1, 2021, and December 31, 2021. Patients aged 18 years and older who were diagnosed with COVID-19 and followed in ICU were included in the study. Patients who have never been vaccinated and patients who have been vaccinated with a single dose were considered unvaccinated. Logistic regression models were fit for the two outcomes (28-day mortality and in-hospital mortality).

RESULTS

A total of 2968 patients were included final analysis. The most of patients followed in the ICU during the study period were unvaccinated (58.5%). Vaccinated patients were older, had higher Charlson comorbidity index (CCI), and had higher APACHE-2 scores than unvaccinated patients. Risk for 28-day mortality and in-hospital mortality was similar in across the year both vaccinated and unvaccinated patients. However, risk for in-hospital mortality and 28-day mortality was higher in the unvaccinated patients in quarter 4 adjusted for gender and CCI (OR: 1.45, 95% CI: 1.06-1.99 and OR: 1.42, 95% CI: 1.03-1.96, respectively) compared to the vaccinated group.

CONCLUSION

Despite effective vaccination, fully vaccinated patients may be admitted to ICU because of disease severity. Unvaccinated patients were younger and had fewer comorbid conditions. Unvaccinated patients have an increased risk of 28-day mortality when adjusted for gender and CCI.

Safety, immunogenicity and protection of heterologous boost with an aerosolised Ad5-nCoV after two-dose inactivated COVID-19 vaccines in adults: a multicentre, open-label phase 3 trial

BACKGROUND

Aerosolised Ad5-nCoV is one of the first licensed mucosal respiratory vaccine against SARS-CoV-2 in the world; however, the safety profile of this vaccine has not been reported in a large population yet.

METHODS

This multicentre, open-label phase 3 trial, done in 15 centres in six provinces (Jiangsu, Hunan, Anhui, Chongqing, Yunnan, Shandong) in China, aimed to evaluate the safety and immunogenicity of aerosolised Ad5-nCoV in healthy adults (members of the general population with no acute febrile disorders, infectious disease, serious cardiovascular diseases, serious chronic diseases or progressive diseases that cannot be controlled) at least 18 years old, who had received two doses of inactivated COVID-19 vaccine as their primary regimen. This study contained a non-randomly assigned safety cohort and a centrally randomly assigned (1:1) immunogenicity subcohort. The patients in the immunogenicity subcohort received aerosolised Ad5-nCov (aerosolised Ad5-nCoV group) or inactivated vaccine (inactivated COVID-19 group) The primary endpoints were the incidence of adverse reactions within 28 days following the booster vaccination with aerosolised Ad5-nCoV in the safety population (collected through a daily record of any solicited or unsolicited adverse events filled by each participant) and the geometric mean titre of neutralising antibodies at day 28 after the booster dose in the immunogenicity subcohort (measured with a pseudovirus neutralisation test). This study was registered with ClinicalTrials.gov, NCT05204589.

FINDINGS

Between Jan 22, 2022, and March 12, 2022, we recruited 11 410 participants who were screened for eligibility, of whom 10 267 (99·8%) participants (5738 [55·9%] men, 4529 [44·1%] women; median age 53 years [18-92]) received the study drugs: 9847 (95·9%) participants in the open-label cohort to receive aerosolised Ad5-nCoV, and 420 (4·1%) in the immunogenicity subcohort (212 in the aerosolised Ad5-nCoV group and 208 in the inactivated vaccine group). Adverse reactions were reported by 1299 (13%) of 10 059 participants within 28 days after receiving the booster vaccination with aerosolised Ad5-nCoV, but most of the adverse reactions reported were mild to moderate in severity. Participants in the aerosolised Ad5-nCoV group had a significantly higher level of the neutralising antibodies against omicron BA.4/5 (GMT 107·7 [95% CI 88·8-130·7]) than did those in the inactivated vaccine group (17·2 [16·3-18·2]) at day 28.

INTERPRETATION

The heterologous booster regimen with aerosolised Ad5-nCoV is safe and highly immunogenic, boosting both systemic and mucosal immunity against omicron subvariants.

FUNDING

National Natural Science Foundation of China, Jiangsu Provincial Science Fund for Distinguished Young Scholars, and Jiangsu Provincial Key Project of Science and Technology Plan.

TRANSLATION

For the Chinese translation of the abstract see Supplementary Materials section.

Immunogenicity and reactogenicity of fractional, heterologous primary COVID-19 vaccination schedules with BNT162b2 boosters in 5-11-year-old Thai children: A multicenter, prospective, double-blind, randomized control trial

OBJECTIVE

To evaluate immunogenicity and safety of heterologous COVID-19 primary vaccination regimens of CoronaVac with fractional and standard BNT162b2 dosages in 5-11-year-old Thai children.

METHODS

This prospective, multicenter, double-blind, randomized control trial divided participants 1:1:1:1 to receive a second dose of either standard (10-μg) or half-dose (5-μg) BNT162b2 vaccines as follows: CoronaVac/10-μg-BNT162b2 (Group 1), CoronaVac/5-μg-BNT162b2 (Group 2), 10-μg-BNT162b2/10-μg-BNT162b2 (Group 3), or 10-μg-BNT162b2/5-μg-BNT162b2 (Group 4). A subset of participants from each arm received 10-μg-BNT162b2 booster (third) doses 16 weeks after their second vaccination. Humoral and cellular immunogenicity were assessed and adverse events (AEs) digitally self-reported.

RESULTS

Of 553 enrolled participants, 50 % were male, the median (interquartile range) age was 8.65 (7.00, 10.00) years, and a majority (91 %) had normal weight-for-height. All participants exhibited similarly robust neutralizing antibodies (NAb) against the ancestral Wuhan strain two weeks after the second vaccination, with titers highest in Group 1 (737.60, 95% CI [654.80, 830.88]), followed by Groups 3 (630.42, 95% CI [555.50, 715.45]), 2 (593.98, 95% CI [506.02, 697.23]), and 4 (451.79, 95% CI [388.62, 525.23]), as well as 56.01 % and 49.68 % seroconversion for BA.1 and BA.5, respectively. Half-dose BNT162b2 as a second dose induced significantly lower NAb titers compared to their respective full-dose regimens (p = 0.03 for Groups 1 vs 2 and p < 0.001 for Groups 3 vs 4). 77.71 % of participants developed SARS-CoV-2 ancestral spike protein-specific T-cell responses two weeks after the second vaccination. This was similar across arms. Booster doses generated NAb titers 5.69-11.51-folds higher than the second vaccination against BA.1. AEs were similar across arms, all mild or moderate, and fully resolved 2-3 days thereafter.

CONCLUSION

Standard and fractional heterologous regimens of CoronaVac-BNT162b2 induced similar or higher humoral immunity than homologous BNT162b2 and represent alternative vaccine regimens for children. These findings are highly relevant in settings concurrently using both vaccines.

Anti-SARS-CoV-2 Antibody Level Is Associated with a History of COVID-19 Infection and mRNA Vaccination in Patients with Diabetes

Type 2 diabetes mellitus (T2DM) is associated with higher severity and mortality in SARS-CoV-2 infections. Vaccination has been encouraged to boost immunity and prevent these unfortunate outcomes. Few studies have evaluated antibody levels after COVID-19 vaccination in patients with T2DM. Therefore, we examined the vaccination status and anti-SARS-CoV-2 antibody levels to identify the factors that affect the antibody levels in patients with T2DM. This cross-sectional study was conducted at the Dr. Hasan Sadikin Hospital and Bandung Kiwari Hospital, Bandung, West Java, Indonesia, between October and November 2022. Adult participants with and without T2DM were tested for SARS-CoV-2 antibodies using a point-of-care quantitative immunochromatographic assay. We enrolled 289 participants: 201 participants with T2DM and 88 participants without T2DM. The T2DM participants had a lower vaccination rate compared with the non-T2DM participants. However, no significant differences in antibody levels were observed between the two groups. Higher antibody levels among the T2DM participants were associated with mRNA vaccination and a history of COVID-19 illness. The lower antibody response observed among the T2DM participants with chronic obstructive pulmonary disease suggests that such patients may need antibody level measurement and an additional booster vaccine.

Immunogenicity of Mix-and-Match CoronaVac/BNT162b2 Regimen versus Homologous CoronaVac/CoronaVac Vaccination: A Single-Blinded, Randomized, Parallel Group Superiority Trial

(1) Background: This study aimed to compare the immunogenicity of the mix-and-match CoronaVac/BNT162b2 vaccination to the homologous CoronaVac/CoronaVac regimen. (2) Methods: We conducted a simple-blinded randomized superiority trial to measure SARS-CoV-2 neutralization antibodies and anti-spike receptor binding domain (RBD) IgG concentrations in blood samples of participants who had received the first dose of CoronaVac vaccine followed by a dose of BNT162b2 or CoronaVac vaccine. The primary endpoint for immunogenicity was the serum-neutralizing antibody level with a percentage of inhibition at 90% at 21-35 days after the boost. A difference of 25% between groups was considered clinically relevant. (3) Results: Among the 240 eligible participants, the primary endpoint data were available for 100 participants randomly allocated to the mix-and-match group versus 99 participants randomly allocated to the homologous dose group. The mix-and-match regimen elicited significantly higher levels of neutralizing antibodies (median level of 96%, interquartile range (IQR) (95-97) versus median level of 94%, IQR (81-96) and anti-spike IgG antibodies (median level of 13,460, IQR (2557-29,930) versus median level of 1190, IQR (347-4964) compared to the homologous group. Accordingly, the percentage of subjects with a percentage of neutralizing antibodies > 90% was significantly higher in the mix-and-match group (90.0%) versus the homologous (60.6%). Interestingly, no severe events were reported within 30 days after the second dose of vaccination in both groups. (4) Conclusions: Our data showed the superiority of the mix-and-match CoronaVac/BNT162b2 vaccination compared to the CoronaVac/CoronaVac regimen in terms of immunogenicity, thus constituting a proof-of-concept study supporting the use of inactivated vaccines in a mix-and-match strategy while ensuring good immunogenicity and safety.

Effectiveness of homologous or heterologous immunization regimens against SARS-CoV-2 after two doses of inactivated COVID-19 vaccine: A systematic review and meta-analysis

We aimed to evaluate the effectiveness or efficacy of heterologous or homologous COVID-19 vaccine regimens against COVID-19-related outcomes after primary immunization with two doses of CoronaVac or Sinopharm COVID-19 vaccines. PubMed, EMBASE, Web of Science, and Cochrane Library databases were searched up to 31 October 2022. The primary measure was vaccine effectiveness against COVID-19 infection with homologous or heterologous booster. The results showed heterologous and homologous booster significantly improved effectiveness against COVID-19 infection compared to primary immunization. The effectiveness against COVID-19 infection was 89.19% (95%CI 78.49, 99.89) for heterologous mRNA vaccine booster, 87.00% (95%CI 82.14, 91.85) for non-replicating vector vaccine booster, 69.99% (95%CI 52.16, 87.82) for homologous booster, and 51.48% (95%CI 41.75, 61.21) for two doses of inactivated vaccine. Homologous and heterologous regimens were also effective against SARS-CoV-2 variants, and more evidence is still needed to confirm our findings.

Effectiveness of first and second boost COVID-19 vaccination in healthy adults during BA.5.2/BF.7 surge in China

With the development of the SARS-CoV-2 pandemic, there have been doubts about the necessity of vaccine boosters for healthy adults. However, due to the lack of relevant evidence, current research is unable to provide reliable medical advice for COVID-19 boost in healthy adults. We conducted a retrospective observational study to evaluate the effectiveness of different COVID-19 vaccination regimens by investigating the SARS-CoV-2 infection status of healthy donors in Southeast China. From December 2022 to February 2023, 737 healthy adult blood donors were analyzed. Results showed that any COVID-19 vaccine boosts reduced the risk of Omicron BA.5.2/BF.7 infection compared to only receiving prime vaccination (rVE = 16%, 95%CI = 4, 27%). The second boost further enhanced vaccine effectiveness compared to the received first booster (rVE = 39%, 95%CI = 16, 55%). Through retrospective observation of healthy adults during the BA.5.2/BF.7 surge in China, we found that boost vaccinations significantly reduce the risk of SARS-CoV-2 infection and disease. Findings show healthy adults benefit from boost vaccinations, even if not at high-risk for severe COVID-19.

Heterologous Booster with BNT162b2 Induced High Specific Antibody Levels in CoronaVac Vaccinees

Immune responses after COVID-19 vaccination should be evaluated in different populations around the world. This study compared antibody responses induced by ChAdOx1 nCoV-19, CoronaVac, and BNT162b2 vaccines. Blood samples from vaccinees were collected pre- and post-vaccinations with the second and third doses. The study enrolled 78 vaccinees, of whom 62.8% were women, with the following median ages: 26 years-ChAdOx1 nCoV-19; 40 years-CoronaVac; 30 years-BNT162b2. Serum samples were quantified for anti-RBD IgG and anti-RBD IgA and anti-spike IgG by ELISA. After two vaccine doses, BNT162b2 vaccinees produced higher levels of anti-RBD IgA and IgG, and anti-spike IgG compared to ChAdOx1 nCoV-19 and CoronaVac vaccinees. The third dose booster with BNT162b2 induced higher levels of anti-RBD IgA and IgG, and anti-spike IgG in CoronaVac vaccinees. Individuals who reported a SARS-CoV-2 infection before or during the study had higher anti-RBD IgA and IgG production. In conclusion, two doses of the studied vaccines induced detectable levels of anti-RBD IgA and IgG and anti-spike IgG in vaccinees. The heterologous booster with BNT162b2 increased anti-RBD IgA and IgG and anti-spike IgG levels in CoronaVac vaccinees and anti-RBD IgA levels in ChAdOx1 nCoV-19 vaccinees. Furthermore, SARS-CoV-2 infection induced higher anti-RBD IgA and IgG levels in CoronaVac vaccinees.

Longer-term effectiveness of a heterologous coronavirus disease 2019 (COVID-19) vaccine booster in healthcare workers in Brazil

Objective

To compare the long-term vaccine effectiveness between those receiving viral vector [Oxford-AstraZeneca (ChAdOx1)] or inactivated viral (CoronaVac) primary series (2 doses) and those who received an mRNA booster (Pfizer/BioNTech) (the third dose) among healthcare workers (HCWs).

Methods

We conducted a retrospective cohort study among HCWs (aged ≥18 years) in Brazil from January 2021 to July 2022. To assess the variation in the effectiveness of booster dose over time, we estimated the effectiveness rate by taking the log risk ratio as a function of time.

Results

Of 14,532 HCWs, coronavirus disease 2019 (COVID-19) was confirmed in 56.3% of HCWs receiving 2 doses of CoronaVac vaccine versus 23.2% of HCWs receiving 2 doses of CoronaVac vaccine with mRNA booster (P < .001), and 37.1% of HCWs receiving 2 doses of ChAdOx1 vaccine versus 22.7% among HCWs receiving 2 doses of ChAdOx1 vaccine with mRNA booster (P < .001). The highest vaccine effectiveness with mRNA booster was observed 30 days after vaccination: 91% for the CoronaVac vaccine group and 97% for the ChAdOx1 vaccine group. Vacine effectiveness declined to 55% and 67%, respectively, at 180 days. Of 430 samples screened for mutations, 49.5% were SARS-CoV-2 delta variants and 34.2% were SARS-CoV-2 omicron variants.

Conclusions

Heterologous COVID-19 vaccines were effective for up to 180 days in preventing COVID-19 in the SARS-CoV-2 delta and omicron variant eras, which suggests the need for a second booster.

Efficacy and effectiveness of inactivated vaccines against symptomatic COVID-19, severe COVID-19, and COVID-19 clinical outcomes in the general population: a systematic review and meta-analysis

Background

Inactivated, whole-virion vaccines have been used extensively in the SARS-CoV-2 pandemic. Its efficacy and effectiveness across regions have not been systematically evaluated. Efficacy refers to how well a vaccine performs in a controlled environment. Effectiveness refers to how well it performs in real world settings.

Methods

This systematic review and meta-analysis reviewed published, peer-reviewed evidence on all WHO-approved inactivated vaccines and evaluated their efficacy and effectiveness against SARS-CoV-2 infection, symptomatic infection, severe clinical outcomes, and severe COVID-19. We searched Pubmed (including MEDLINE), EMBASE (via OVID), Web of Science Core Collection, Web of Science Chinese Science Citation Database, and Clinicaltrials.gov.

Findings

The final pool included 28 studies representing over 32 million individuals reporting efficacy or effectiveness estimates of complete vaccination using any approved inactivated vaccine between January 1, 2019 and June 27, 2022. Evidence was found for efficacy and effectiveness against symptomatic infection (OR 0.21, 95% CI 0.16-0.27, I2 = 28% and OR 0.32, 95% CI 0.16-0.64, I2 = 98%, respectively) and infection (OR 0.53, 95% CI 0.49-0.57, I2 = 90% and OR 0.31, 95% CI 0.24-0.41, I2 = 0%, respectively) for early SARS-CoV-2 variants of concern (VoCs) (Alpha, Delta), and for waning of vaccine effectiveness with more recent VoCs (Gamma, Omicron). Effectiveness remained robust against COVID-related ICU admission (OR 0.21, 95% CI 0.04-1.08, I2 = 99%) and death (OR 0.08, 95% CI 0.00-2.02, I2 = 96%), although effectiveness estimates against hospitalization (OR 0.44, 95% CI 0.37-0.53, I2 = 0%) were inconsistent.

Interpretation

This study showed evidence of efficacy and effectiveness of inactivated vaccines for all outcomes, although inconsistent reporting of key study parameters, high heterogeneity of observational studies, and the small number of studies of particular designs for most outcomes undermined the reliability of the findings. Findings highlight the need for additional research to address these limitations so that more definitive conclusions can be drawn to inform SARS-CoV-2 vaccine development and vaccination policies.

Funding

Health and Medical Research Fund on COVID-19, Health Bureau of the Government of the Hong Kong SAR.

Heterologous vaccination with inactivated vaccine and mRNA vaccine augments antibodies against both spike and nucleocapsid proteins of SARS-CoV-2: a local study in Macao

The mRNA vaccines (RVs) can reduce the severity and mortality of severe acute respiratory syndrome coronavirus (SARS-CoV-2). However, almost only the inactivated vaccines (IVs) but no RVs had been used in mainland China until most recently, and the relaxing of its anti-pandemic strategies in December 2022 increased concerns about new outbreaks. In comparison, many of the citizens in Macao Special Administrative Region of China received three doses of IV (3IV) or RV (3RV), or 2 doses of IV plus one booster of RV (2IV+1RV). By the end of 2022, we recruited 147 participants with various vaccinations in Macao and detected antibodies (Abs) against the spike (S) protein and nucleocapsid (N) protein of the virus as well as neutralizing antibodies (NAb) in their serum. We observed that the level of anti-S Ab or NAb was similarly high with both 3RV and 2IV+1RV but lower with 3IV. In contrast, the level of anti-N Ab was the highest with 3IV like that in convalescents, intermediate with 2IV+1RV, and the lowest with 3RV. Whereas no significant differences in the basal levels of cytokines related to T-cell activation were observed among the various vaccination groups before and after the boosters. No vaccinees reported severe adverse events. Since Macao took one of the most stringent non-pharmaceutical interventions in the world, this study possesses much higher confidence in the vaccination results than many other studies from highly infected regions. Our findings suggest that the heterologous vaccination 2IV+1RV outperforms the homologous vaccinations 3IV and 3RV as it induces not only anti-S Ab (to the level as with 3RV) but also anti-N antibodies (via the IV). It combines the advantages of both RV (to block the viral entry) and IV (to also intervene the subsequent pathological processes such as intracellular viral replication and interference with the signal transduction and hence the biological functions of host cells).

Effectiveness and safety of coronavirus disease 2019 vaccines

PURPOSE OF REVIEW

To review and summarise recent evidence on the effectiveness of coronavirus disease 2019 (COVID-19) vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and COVID-19 hospitalisation and death in adults as well as in specific population groups, namely pregnant women, and children and adolescents. We also sought to summarise evidence on vaccine safety in relation to cardiovascular and neurological complications. In order to do so, we drew primarily on evidence from two our own data platforms and supplement these with insights from related large population-based studies and systematic reviews.

RECENT FINDINGS

All studies showed high vaccine effectiveness against confirmed SARS-CoV-2 infection and in particular against COVID-19 hospitalisation and death. However, vaccine effectiveness against symptomatic COVID-19 infection waned over time. These studies also found that booster vaccines would be needed to maintain high vaccine effectiveness against severe COVID-19 outcomes. Rare cardiovascular and neurological complications have been reported in association with COVID-19 vaccines.

SUMMARY

The findings from this paper support current recommendations that vaccination remains the safest way for adults, pregnant women, children and adolescents to be protected against COVID-19. There is a need to continue to monitor the effectiveness and safety of COVID-19 vaccines as these continue to be deployed in the evolving pandemic.

Robust specific RBD responses and neutralizing antibodies after ChAdOx1 nCoV-19 and CoronaVac vaccination in SARS-CoV-2- seropositive individuals

Background

The pandemic unleashed by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected more than 500 million people worldwide and caused more than 6 million deaths. Cellular and humoral immunity induced by infection or immunization are key factors in controlling the viral burden and avoiding the recurrence of coronavirus disease. The duration and effectiveness of immunity after infection is relevant to pandemic policy interventions, including the timing of vaccine boosters.

Objectives

We sought to evaluate longitudinal binding and functional antibodies against SARS-CoV-2 receptor-binding domain in police officers and health care workers with a history of coronavirus disease 2019 and compare with SARS-CoV-2-naive individuals after vaccination with adenovirus-based ChAdOx1 nCoV-19 (AstraZeneca-Fiocruz) or the inactivated CoronaVac vaccine (Sinovac-Butantan Institute).

Methods

A total of 208 participants were vaccinated. Of these, 126 (60.57%) received the ChAdOx1 nCoV-19 vaccine and 82 (39.42%) received the CoronaVac vaccine. Prevaccination and postvaccination blood was collected, and the amount of anti-SARS-CoV-2 IgG and the neutralizing ability of the antibodies to block the interaction between angiotensin-converting enzyme 2 and receptor-binding domain were determined.

Results

Subjects with preexisting SARS-CoV-2 immunity and who received a single dose of ChAdOx1 nCoV-19 or CoronaVac have similar or superior antibody levels when compared with levels in seronegative individuals even after 2 doses of the vaccine. Neutralizing antibody titers of seropositive individuals were higher with a single dose of either ChAdOx1 nCoV-19 or CoronaVac compared with those of seronegative individuals. After 2 doses, both groups reached a plateau response.

Conclusions

Our data reinforce the importance of vaccine boosters to increase specific binding and neutralizing SARS-CoV-2 antibodies.

Effectiveness of COVID-19 Vaccination Against SARS-CoV-2 Omicron Variant Infection and Symptoms - China, December 2022-February 2023

What is already known about this topic?

A considerable percentage of the population has received both primary and booster vaccinations, which could potentially provide protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron infections and related symptoms.

What is added by this report?

The self-reported infection rate, as determined from an online survey, reached its peak (15.5%) between December 19 and 21, 2022, with an estimated 82.4% of individuals in China being infected as of February 7, 2023. During the epidemic, the effectiveness of booster vaccinations against SARS-CoV-2 Omicron infection was found to be 49.0% within three months of vaccination and 37.9% between 3 and 6 months following vaccination. Furthermore, the vaccine effectiveness of the booster vaccination in relation to symptom prevention varied from 48.7% to 83.2% within three months and from 25.9% to 69.0% between 3 and 6 months post-booster vaccination.

What are the implications for public health practice?

The development and production of efficacious vaccines, together with prompt vaccinations or emergency vaccinations, have the potential to mitigate the epidemic's impact and safeguard public health.

Vaccine effectiveness of BNT162b2 and CoronaVac against SARS-CoV-2 omicron infection and related hospital admission among people with substance use disorder in Hong Kong: a matched case-control study

BACKGROUND

People with substance use disorder have a high risk of SARS-CoV-2 infection and subsequent poor outcomes. Few studies have evaluated COVID-19 vaccine effectiveness among people with substance use disorder. We aimed to estimate the vaccine effectiveness of BNT162b2 (Fosun-BioNTech) and CoronaVac (Sinovac) against SARS-CoV-2 omicron (B.1.1.529) infection and related hospital admission in this population.

METHODS

We did a matched case-control study using electronic health databases in Hong Kong. Individuals diagnosed with substance use disorder between Jan 1, 2016, and Jan 1, 2022, were identified. People aged 18 years and older with SARS-CoV-2 infection from Jan 1 to May 31, 2022, and people with COVID-19-related hospital admission from Feb 16 to May 31, 2022, were included as cases and were matched by age, sex, and previous clinical history with controls from all individuals diagnosed with substance use disorder who attended the Hospital Authority health services: up to three controls for SARS-CoV-2 infection and up to ten controls for hospital admission. Conditional logistical regression was used to evaluate the association between vaccination status (ie, one, two, or three doses of BNT162b2 or CoronaVac) and the risk of SARS-CoV-2 infection and COVID-19-related hospital admission, adjusted for baseline comorbidities and medication use.

FINDINGS

Among 57 674 individuals with substance use disorder, 9523 people with SARS-CoV-2 infections (mean age 61·00 years, SD 14·90; 8075 [84·8%] males and 1448 [15·2%] females) were identified and matched to 28 217 controls (mean age 60·99 years, 14·67; 24 006 [85·1%] males and 4211 [14·9%] females), and 843 people with COVID-19-related hospital admissions (mean age 70·48 years, SD 14·68; 754 [89·4%] males and 89 [10·6%] females) were identified and matched to 7459 controls (mean age 70·24 years, 13·87; 6837 [91·7%] males and 622 [8·3%] females). Data on ethnicity were not available. We observed significant vaccine effectiveness against SARS-CoV-2 infection for two-dose BNT162b2 vaccination (20·7%, 95% CI 14·0-27·0, p<0·0001) and three-dose vaccination (all BNT162b2 41·5%, 34·4-47·8, p<0·0001; all CoronaVac 13·6%, 5·4-21·0, p=0·0015; BNT162b2 booster after two-dose CoronaVac 31·3%, 19·8-41·1, p<0·0001), but not for one dose of either vaccine or two doses of CoronaVac. Significant vaccine effectiveness against COVID-19-related hospital admission was detected after one dose of BNT162b2 vaccination (35·7%, 3·8-57·1, p=0·032), two-dose vaccination (both BNT162b2 73·3%, 64·3 to 80·0, p<0·0001; both CoronaVac 59·9%, 50·2-67·7, p<0·0001), and three-dose vaccination (all BNT162b2 86·3%, 75·6-92·3, p<0·0001; all CoronaVac 73·5% 61·0-81·9, p<0·0001; BNT162b2 booster after two-dose CoronaVac 83·7%, 64·6-92·5, p<0·0001), but not after one dose of CoronaVac.

INTERPRETATION

For both BNT162b2 and CoronaVac, two-dose or three-dose vaccination was protective against COVID-19-related hospital admission and the booster dose provided protection against SARS-CoV-2 infection among people with substance use disorder. Our findings confirm the importance of booster doses in this population during the period dominated by the omicron variant.

FUNDING

Health Bureau, the Government of the Hong Kong Special Administrative Region.

Age-dependent final size equation to anticipate mortality impact of COVID-19 in China

Before reopening society in December 2022, China had not achieved sufficiently high vaccination coverage among people aged 80 years and older, who are vulnerable to severe infection and death owing to COVID-19. Suddenly ending the zero-COVID policy was anticipated to lead to substantial mortality. To investigate the mortality impact of COVID-19, we devised an age-dependent transmission model to derive a final size equation, permitting calculation of the expected cumulative incidence. Using an age-specific contact matrix and published estimates of vaccine effectiveness, final size was computed as a function of the basic reproduction number, R0. We also examined hypothetical scenarios in which third-dose vaccination coverage was increased in advance of the epidemic, and also in which mRNA vaccine was used instead of inactivated vaccines. Without additional vaccination, the final size model indicated that a total of 1.4 million deaths (half of which were among people aged 80 years and older) were anticipated with an assumed R0 of 3.4. A 10% increase in third-dose coverage would prevent 30,948, 24,106, and 16,367 deaths, with an assumed second-dose effectiveness of 0%, 10%, and 20%, respectively. With mRNA vaccine, the mortality impact would have been reduced to 1.1 million deaths. The experience of reopening in China indicates the critical importance of balancing pharmaceutical and non-pharmaceutical interventions. Ensuring sufficiently high vaccination coverage is vital in advance of policy changes.

Real-world effectiveness and factors associated with effectiveness of inactivated SARS-CoV-2 vaccines: a systematic review and meta-regression analysis

BACKGROUND

The two inactivated SARS-CoV-2 vaccines, CoronaVac and BBIBP-CorV, have been widely used to control the COVID-19 pandemic. The influence of multiple factors on inactivated vaccine effectiveness (VE) during long-term use and against variants is not well understood.

METHODS

We selected published or preprinted articles from PubMed, Embase, Scopus, Web of Science, medRxiv, BioRxiv, and the WHO COVID-19 database by 31 August 2022. We included observational studies that assessed the VE of completed primary series or homologous booster against SARS-CoV-2 infection or severe COVID-19. We used DerSimonian and Laird random-effects models to calculate pooled estimates and conducted multiple meta-regression with an information theoretic approach based on Akaike's Information Criterion to select the model and identify the factors associated with VE.

RESULTS

Fifty-one eligible studies with 151 estimates were included. For prevention of infection, VE associated with study region, variants, and time since vaccination; VE was significantly decreased against Omicron compared to Alpha (P = 0.021), primary series VE was 52.8% (95% CI, 43.3 to 60.7%) against Delta and 16.4% (95% CI, 9.5 to 22.8%) against Omicron, and booster dose VE was 65.2% (95% CI, 48.3 to 76.6%) against Delta and 20.3% (95% CI, 10.5 to 28.0%) against Omicron; primary VE decreased significantly after 180 days (P = 0.022). For the prevention of severe COVID-19, VE associated with vaccine doses, age, study region, variants, study design, and study population type; booster VE increased significantly (P = 0.001) compared to primary; though VE decreased significantly against Gamma (P = 0.034), Delta (P = 0.001), and Omicron (P = 0.001) compared to Alpha, primary and booster VEs were all above 60% against each variant.

CONCLUSIONS

Inactivated vaccine protection against SARS-CoV-2 infection was moderate, decreased significantly after 6 months following primary vaccination, and was restored by booster vaccination. VE against severe COVID-19 was greatest after boosting and did not decrease over time, sustained for over 6 months after the primary series, and more evidence is needed to assess the duration of booster VE. VE varied by variants, most notably against Omicron. It is necessary to ensure booster vaccination of everyone eligible for SARS-CoV-2 vaccines and continue monitoring virus evolution and VE.

TRIAL REGISTRATION

PROSPERO, CRD42022353272.

Narrative Review of the Evolution of COVID-19 Vaccination Recommendations in Countries in Latin America, Africa and the Middle East, and Asia

The rapid rollout of vaccines to combat the coronavirus disease 2019 (COVID-19) pandemic over the past 2 years has resulted in the use of various vaccine platforms and regional differences in COVID-19 vaccine implementation strategies. The aim of this narrative review was to summarize evolving COVID-19 vaccine recommendations in countries in Latin America, Asia, and Africa and the Middle East across various vaccine platforms, age groups, and specific subpopulations. Nuances in primary and booster vaccination schedules were evaluated, and the preliminary impact of such diverse vaccination strategies are discussed, including key vaccine effectiveness data in the era of Omicron-lineage variants. Primary vaccination rates for included Latin American countries were 71-94% for adults and between 41% and 98% for adolescents and children; rates for first booster in adults were 36-85%. Primary vaccination rates for adults in the included Asian countries ranged from 64% in the Philippines to 98% in Malaysia, with corresponding booster rates varying from 9% in India to 78% in Singapore; for adolescents and children, primary vaccination rates ranged from 29% in the Philippines to 93% in Malaysia. Across included African and Middle Eastern countries, primary vaccination rates in adults varied widely from 32% in South Africa to 99% in the United Arab Emirates; booster rates ranged from 5% in South Africa to 60% in Bahrain. Evidence from the regions studied indicates preference of using an mRNA vaccine as a booster on the basis of safety and effectiveness of observed real-world data, especially during circulation of Omicron lineages. Vaccination against COVID-19 remains of paramount importance to reduce the burden of disease; strategies to overcome vaccine inequity, fatigue, hesitancy, and misinformation and to ensure adequate access and supply are also important.

Comparison of Biological, Pharmacological Characteristics, Indications, Contraindications, Efficacy, and Adverse Effects of Inactivated Whole-Virus COVID-19 Vaccines Sinopharm, CoronaVac, and Covaxin: An Observational Study

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an emerging viral zoonotic illness that has developed a distinctive and threatening situation globally. Worldwide, many vaccines were introduced to fight against the COVID-19 pandemic. The present study aims to compare the bio-pharmacological characteristics, indications, contraindications, efficacy, and adverse effects of inactivated whole-virus COVID-19 vaccines, Sinopharm, CoronaVac, and Covaxin. Initially, 262 documents and 6 international organizations were selected. Finally, 41 articles, fact sheets, and international organizations were included. The data were recorded from the World Health Organization (WHO), Food and Drug Administration (FDA) USA, Web of Science, PubMed, EMBASE, and Scopus. The results demonstrated that these three inactivated whole-virus COVID-19 vaccines, Sinopharm, CoronaVac, and Covaxin, received emergency approval from the FDA/WHO, and all three of these vaccines are beneficial for the prevention of the COVID-19 pandemic. The Sinopharm vaccine has been recommended during pregnancy and for people of all age groups, and the CoronaVac and Covaxin vaccines are recommended for people over 18 years of age and older. These three vaccines have recommended intramuscular doses of 0.5 mL each, with a 3-4 week interval. These three vaccines can be stored in a refrigerator at +2 to +8 °C. The common adverse effects of these vaccines are pain at the injection site, redness, fatigue, headache, myalgias, general lethargy, body ache, arthralgia, nausea, chills, fever, and dizziness. The overall mean efficiency for the prevention of the COVID-19 disease is 73.78% for Sinopharm, 70.96% for CoronaVac, and 61.80% for Covaxin. In conclusion, all three inactivated whole-virus COVID-19 vaccines, Sinopharm, CoronaVac, and Covaxin, are beneficial for the prevention of the COVID-19 pandemic. However, evidence suggests that the overall impact of Sinopharm is slightly better than that of CoronaVac and Covaxin.

Attitudes and concerns regarding booster dose of COVID-19 vaccine among Egyptian patients with autoimmune and rheumatic diseases: a cross-sectional survey study

BACKGROUND

COVID-19 booster dose vaccination acceptance and actual vaccination behavior is not known among Egyptian individuals with autoimmune and rheumatic diseases (ARDs). The aim of this study was to investigate the acceptability of booster dose of the COVID-19 vaccine, as well as the factors that drive and inhibit that acceptance among Egyptian patients diagnosed with ARDs.

METHODS

This interview-based, cross-sectional analytical study was carried out on ARD patients from 20 July to 20 November 2022. A questionnaire was created to assess sociodemographic and clinical data, as well as COVID-19 vaccination status and the intention to receive a COVID-19 vaccine booster dose, perception of health benefits of it in addition to the perceived barriers and/or concerns.

RESULTS

A total of 248 ARD patients were included, with a mean age of 39.8 years (SD = 13.2), and 92.3% were females. Among them, 53.6% were resistant to the COVID-19 booster dose, whereas 31.9% were acceptant and 14.5% were hesitant. Those who were administering corticosteroids and hydroxychloroquine shown significantly greater booster hesitancy and resistance (p = 0.010 and 0.004, respectively). The primary motivation for taking a booster dose among the acceptant group was own volition (92%). Most acceptants believed that booster dose can prevent serious infection (98.7%) and community spread (96.2%). Among the hesitant and resistant groups, the main concerns for booster dose were fear about its major adverse effects (57.4%) and long-term impact (45.6%).

CONCLUSIONS

There is a low acceptability rate of booster dose of COVID-19 vaccine among Egyptian patients with ARD diseases. Public health workers and policymakers need to make sure that all ARD patients get clear messages about accepting the COVID-19 booster dose.

The effectiveness of COVID-19 vaccines against severe cases and deaths in Brazil from 2021 to 2022: a registry-based study

Background

Brazil started the COVID-19 mass vaccination in January 2021 with CoronaVac and ChAdOx1, followed by BNT162b2 and Ad26.COV2.S vaccines. By the end of 2021, more than 317 million vaccine doses were administered in the adult population. This study aimed at estimating the effectiveness of the primary series of COVID-19 vaccination and booster shots in protecting against severe cases and deaths in Brazil during the first year of vaccination.

Methods

A cohort dataset of over 158 million vaccination and severe cases records linked from official national registries was analyzed via a mixed-effects Poisson model, adjusted for age, state of residence, time after immunization, and calendar time to estimate the absolute vaccine effectiveness of the primary series of vaccination and the relative effectiveness of the booster. The method permitted analysis of effectiveness against hospitalizations and deaths, including in the periods of variant dominance.

Findings

Vaccine effectiveness against severe cases and deaths remained over 25% and 50%, respectively, after 19 weeks from primary vaccination of BNT162b2, ChAdOx1, or CoronaVac vaccines. The boosters conferred greater protection than the primary series of vaccination, with heterologous boosters providing marginally greater protection than homologous. The effectiveness against hospitalization during the Omicron dominance in the 60+ years old population started at 61.7% (95% CI, 26.1-86.2) for ChAdOx1, 95.6% (95% CI, 82.4-99.9) for CoronaVac, and 72.3% (95% CI, 51.4-87.4) for the BNT162b2 vaccine.

Interpretation

This study provides real-world evidence of the effectiveness of COVID-19 vaccination in Brazil, including during the Omicron wave, demonstrating protection even after waning effectiveness. Comparisons of the effectiveness among different vaccines require caution due to potential bias effects related to age groups, periods in the pandemic, and eventual behavioural changes.

Funding

Fundação Oswaldo Cruz (FIOCRUZ), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ), Pan American Health Organization (PAHO), Departamento de Ciência e Tecnologia da Secretaria de Ciência, Tecnologia, Inovação e Insumos Estratégicos em Saúde do Ministério da Saúde do Brasil (DECIT/SCTIE/MS).

Simulating potential outbreaks of Delta and Omicron variants based on contact-tracing data: A modelling study in Fujian Province, China

Although studies have compared the relative severity of Omicron and Delta variants by assessing the relative risks, there are still gaps in the knowledge of the potential COVID-19 burden these variations may cause. And the contact patterns in Fujian Province, China, have not been described. We identified 8969 transmission pairs in Fujian, China, by analyzing a contact-tracing database that recorded a SARS-CoV-2 outbreak in September 2021. We estimated the waning vaccine effectiveness against Delta variant infection, contact patterns, and epidemiology distributions, then simulated potential outbreaks of Delta and Omicron variants using a multi-group mathematical model. For instance, in the contact setting without stringent lockdowns, we estimated that in a potential Omicron wave, only 4.7% of infections would occur in Fujian Province among individuals aged >60 years. In comparison, 58.75% of the death toll would occur in unvaccinated individuals aged >60 years. Compared with no strict lockdowns, combining school or factory closure alone reduced cumulative deaths of Delta and Omicron by 28.5% and 6.1%, respectively. In conclusion, this study validates the need for continuous mass immunization, especially among elderly aged over 60 years old. And it confirms that the effect of lockdowns alone in reducing infections or deaths is minimal. However, these measurements will still contribute to lowering peak daily incidence and delaying the epidemic, easing the healthcare system's burden.

Three-dose vaccination-induced immune responses protect against SARS-CoV-2 Omicron BA.2: a population-based study in Hong Kong

Background

The ongoing outbreak of SARS-CoV-2 Omicron BA.2 infections in Hong Kong, the model city of universal masking of the world, has resulted in a major public health crisis. Although the third vaccination resulted in strong boosting of neutralization antibody, vaccine efficacy and correlate of immune protection against the major circulating Omicron BA.2 remain to be investigated.

Methods

We investigated the vaccine efficacy against the Omicron BA.2 breakthrough infection among 470 public servants who had received different SARS-CoV-2 vaccine regimens including two-dose BNT162b2 (2 × BNT, n = 169), three-dose BNT162b2 (3 × BNT, n = 168), two-dose CoronaVac (2 × CorV, n = 34), three-dose CoronaVac (3 × CorV, n = 67) and third-dose BNT162b2 following 2 × CorV (2 × CorV+1BNT, n = 32). Humoral and cellular immune responses after three-dose vaccination were further characterized and correlated with clinical characteristics of BA.2 infection.

Findings

During the BA.2 outbreak, 27.7% vaccinees were infected. The timely third-dose vaccination provided significant protection with lower incidence rates of breakthrough infections (2 × BNT 46.2% vs 3 × BNT 13.1%, p < 0.0001; 2 × CorV 44.1% vs 3 × CorV 19.4%, p = 0.003). Investigation of immune responses on blood samples derived from 90 subjects in three-dose vaccination cohorts collected before the BA.2 outbreak revealed that the third-dose vaccination activated spike (S)-specific memory B cells and Omicron cross-reactive T cell responses, which correlated with reduced frequencies of breakthrough infections and disease severity rather than with types of vaccines. Moreover, the frequency of S-specific activated memory B cells was significantly lower in infected vaccinees than uninfected vaccinees before vaccine-breakthrough infection whereas IFN-γ+ CD4 T cells were negatively associated with age and viral clearance time. Critically, BA.2 breakthrough infection boosted cross-reactive memory B cells with enhanced cross-neutralizing antibodies to Omicron sublineages, including BA.2.12.1 and BA.4/5, in all vaccinees tested.

Interpretation

Our results imply that the timely third vaccination and immune responses are likely required for vaccine-mediated protection against Omicron BA.2 pandemic. Although BA.2 conferred the highest neutralization resistance compared with variants of concern tested before the emergence of BA.2.12.1 and BA.4/5, the third dose vaccination-activated S-specific memory B cells and Omicron cross-reactive T cell responses contributed to reduced frequencies of breakthrough infection and disease severity. Neutralizing antibody potency enhanced by BA.2 breakthrough infection in vaccinees with prior 3 doses of CoronaVac or BNT162b2 may reduce the risk of infection against ongoing BA.2.12.1 and BA.4/5.

Funding

Hong Kong Research Grants Council Collaborative Research Fund, Health and Medical Research Fund, Wellcome Trust, Shenzhen Science and Technology Program, the Health@InnoHK, Innovation and Technology Commission of Hong Kong, China, National Program on Key Research Project, Emergency Key Program of Guangzhou Laboratory, donations from the Friends of Hope Education Fund and the Hong Kong Theme-Based Research Scheme.

Estimated COVID-19 severe cases and deaths averted in the first year of the vaccination campaign in Brazil: A retrospective observational study

Background

A nationwide Severe Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) vaccination campaign was initiated in Brazil in January 2021 with CoronaVac (Sinovac Biotech) and ChAdOx1 nCoV-19 (AstraZeneca) followed by BNT162b2 mRNA (Pfizer-BioNTech) and Ad26.COV2.S (Johnson & Johnson-Janssen) vaccines. Here we provide estimates of the number of severe cases and deaths due to coronavirus disease (COVID-19) averted during the first year of the mass vaccination campaign in Brazil.

Methods

Data on COVID-19 vaccination and COVID-19-related illness and death were obtained from the Brazilian Ministry of Health and used to estimate the direct effects of the vaccination campaign on the number of severe cases and deaths due to COVID-19 occurring between January 17, 2021 and January 31, 2022. To this end, we compared the daily age-specific rates between the unvaccinated population and the "at least partly vaccinated" population (received at least one dose of a two-dose vaccine), as well as other two vaccination subgroups, "fully vaccinated" (completed the one- or two-dose vaccine schedule), and "boosted-vaccinated" (fully vaccinated and recipients of booster dose) populations.

Findings

We estimated that 74% (n = 875,846; 95% confidence interval, CI 843,383-915,709) of total expected cases of severe COVID-19 and 82% (n = 303,129; 95% CI 284,019-321,681) of total expected deaths due to COVID-19 were averted in the first year of the national vaccination campaign. The averted burden was heterogeneous between age groups and higher in the more populous states. However, outcome rate differences between vaccinated and unvaccinated groups were higher in the less populated states.

Interpretation

The first year of the COVID-19 vaccination program in Brazil saved the lives of at least 303,129 adults. The results highlight the need for future vaccination campaigns, including those required in the current pandemic, to rapidly achieve high uptake, particularly among the elderly and residents of the least populous regions.

Funding

Ministry of Health (Brazil).

CoronaVac, BNT162b2 and heterologous COVID-19 vaccine outcomes in patients with ventricular assist device

BACKGROUND

A consensus has not yet been reached regarding which COVID-19 vaccine program should be applied in patients with ventricular assist device (VAD). Our aim was to assess the clinical outcome of inactivated, mRNA and heterologous vaccine program in patient with VAD.

METHODS

In this retrospective and cross-sectional study; adult patients who underwent VAD implantation between January 2012 and September 2021 and received any vaccine that were used in Republic of Türkiye for COVID-19, were included. The patients were divided into three groups according to the type of vaccine; "inactivated," "mRNA" and "heterologous." Clinical outcomes were analyzed.

RESULTS

Eighteen patients were in each group in the "inactivated," "mRNA" and "heterologous" groups. Mean age was 51.6 ± 12 years in "inactivated" group, 42.5 ± 15.5 years in "mRNA" group and 41.1 ± 15.4 years in "heterologous" group. There was no significant difference between the groups in age, gender, body surface area, body mass index and etiology (p > 0.05). After last dose of vaccines, the number of patients had COVID-19 positive test were three (16.7%), one (5.6%), and two (11.1%) in "inactivated," "mRNA" and "heterologous" groups, respectively. Pump thrombosis was seen in two patients in "mRNA" group and one patient in "heterologous" group. No pump thrombosis was seen in "inactivated" group. COVID-19-related death or intubation was not observed.

CONCLUSION

All vaccine that used for COVID-19 are safe and effective in patients with VAD. In countries that give priority to inactivated vaccines, mRNA vaccines may then be made as boosters.

Effectiveness of BNT162b2 and CoronaVac vaccinations against SARS-CoV-2 omicron infection in people aged 60 years or above: a case-control study

BACKGROUND

In view of limited evidence that specifically addresses vaccine effectiveness (VE) in the older population, this study aims to evaluate the real-world effectiveness of BNT162b2 and CoronaVac in older adults during the Omicron BA.2 outbreak.

METHODS

This case-control study analyzed data available between January and March 2022 from the electronic health databases in Hong Kong and enrolled individuals aged 60 or above. Each case was matched with up to 10 controls by age, sex, index date and Charlson Comorbidity Index for the four outcomes (COVID-19 infection, COVID-19-related hospitalization, severe complications, and all-cause mortality) independently. Conditional logistic regression was conducted to evaluate VE of BNT162b2 and CoronaVac against COVID-19-related outcomes within 28 days after COVID-19 infection among participants stratified by age groups (60-79, ≥80 years old).

RESULTS

A dose-response relationship between the number of vaccine doses received and protection against severe or fatal disease was observed. Highest VE (95% CI) against COVID-19 infection was observed in individuals aged ≥80 who received three doses of BNT162b2 [75.5% (73.1-77.7%)] or three doses of CoronaVac [53.9% (51.0-56.5%)] compared to those in the younger age group who received three doses of BNT162b2 [51.1% (49.9-52.4%)] or three doses of CoronaVac [2.0% (-0.1-4.1%)]. VE (95% CI) was higher for other outcomes, reaching 91.9% (89.4-93.8%) and 86.7% (84.3-88.8%) against COVID-19-related hospitalization; 85.8% (61.2-94.8%) and 89.8% (72.4-96.3%) against COVID-19-related severe complications; and 96.4% (92.9-98.2%) and 95.0% (92.1-96.8%) against COVID-19-related mortality after three doses of BNT162b2 and CoronaVac in older vaccine recipients, respectively. A similar dose-response relationship was established in younger vaccine recipients and after stratification by sex and Charlson Comorbidity Index.

CONCLUSION

Both BNT162b2 and CoronaVac vaccination were effective in protecting older adults against COVID-19 infection and COVID-19-related severe outcomes amidst the Omicron BA.2 pandemic, and VE increased further with the third dose.

Population-Based Analysis of the Immunoglobulin G Response to Different COVID-19 Vaccines in Brazil

(1) Background: COVID-19 vaccination in Brazil has been performed mostly with CoronaVac (Sinovac), ChAdOx1-S (AstraZeneca-University of Oxford) and BNT162b2 (Pfizer-BioNTech) vaccines. The titers of IgG antibodies reactive to the SARS-CoV-2 spike protein correlate with vaccine efficacy. Studies comparing vaccine immunogenicity in a real-world scenario are lacking. (2) Methods: We performed a population-based study to analyze the immunoglobulin G response to different COVID-19 vaccines. Citizens older than 18 years (n = 2376) provided personal data, a self-declaration of any previous COVID-19 positive tests and information regarding COVID-19 vaccination: the vaccine popular name and the date of each dose. Blood samples were collected and the levels of IgG reactive to SARS-CoV-2 antigens were determined and compared between different vaccine groups. (3) Results: The seroconversion for anti-spike IgG achieved > 95% by February 2022 and maintained stable until June 2022. Higher anti-spike IgG titers were detected in individuals vaccinated with BNT162b2, followed by ChAdOx1-S and CoronaVac. The anti-spike IgG response was negatively correlated with age and interval after the second dose for the BNT162b2 vaccine. Natural infections boosted anti-spike IgG in those individuals who completed primary vaccination with ChAdOx1-S and CoronaVac, but not with BNT162b2. The levels of anti-spike IgG increased with the number of vaccine doses administered. The application of BNT162b2 as a 3rd booster dose resulted in high anti-spike IgG antibody titers, despite the type of vaccine used during primary vaccination. (4) Conclusions: Our data confirmed the effectiveness of the Brazilian vaccination program. Of the vaccines used in Brazil, BNT162b2 performed better to elicit anti-spike protein IgG after primary vaccination and as a booster dose and thus should be recommended as a booster whenever available. A continuous COVID-19 vaccination program will be required to sustain anti-spike IgG antibodies in the population.

A review of COVID vaccines: success against a moving target

BACKGROUND

Multiple vaccine platforms against COVID-19 have been developed and found safe and efficacious at a record speed. Although most are effective, they vary in their ease of production and distribution, their potential speed of modification against new variants, and their durability of protection and safety in certain target groups.

SOURCES OF DATA

Our discussion is based on published reports of clinical trials and analyses from national and global health agencies.

AREAS OF AGREEMENT

The production of neutralizing antibodies against the viral spike protein is protective, and all vaccines for which published data exist have been found to be effective against severe disease caused by the viral strain they target.

AREAS OF CONTROVERSY

The degree to which vaccines protect against emerging variants, moderate disease and asymptomatic infection remains somewhat unclear.

GROWING POINTS

Knowledge of the duration of protection and its decay is increasing, and discussions of booster frequency and target strains are ongoing.

AREAS TIMELY FOR DEVELOPING RESEARCH

The global effort to combat transmission and disease continues to rely upon intense epidemiological surveillance, whilst real-world data and clinical trials shape vaccination schedules and formulae.

COVID-19 in elderly: Correlations of viral load, clinical course, laboratory parameters, among patients vaccinated with CoronaVac

SARS-CoV-2 virus was initially identified in Wuhan, China, in December 2019 and a global pandemic was declared in March 2020 by World Health Organization. COVID-19 disease is characterized with severe pneumonia and hypoxemia, especially in the elderly population. The elderly population was primarily vaccinated with CoronaVac, which is a whole virion inactivated vaccine (Sinovac Biotech, China) in Turkey. This study aimed to investigate the association of viral load and laboratory parameters with the severity of the disease and vaccination status in elderly (older than 60 years old) COVID-19 patients. The age range of the patients was 61-97 years old with a mean of 71.80. Vaccinated patients had a lower viral load (P = 0.253) in nasopharyngeal swabs during breakthrough COVID-19 infection compared to unvaccinated ones and were hospitalized for a shorter period of time in hospital wards (P = 0.035). A lower number of patients were vaccinated in both moderate (n = 33, 29.20%) and severe/critical group (n = 46, 34.07%) (P = 0.412). Only 17 (32.08%) vaccinated patients were hospitalized in an intensive care unit (ICU), whereas 36 (67.92%) of the ICU patients were unvaccinated (P = 0.931). Severe/critical patients had higher c-reactive protein (CRP), platelet-to-lymphocyte ratio (PLR), fibrinogen, ferritin, and lactate dehydrogenase (LDH) levels compared to the moderate group on the admission day (P < 0.05). Our study suggested that elderly patients vaccinated with CoronaVac had a shorter stay in hospitals and according to our results CRP, PLR, fibrinogen, ferritin, and LDH levels could be used to determine the severity of the infections.

CoronaVac: A review of efficacy, safety, and immunogenicity of the inactivated vaccine against SARS-CoV-2

CoronaVac, also known as the Sinovac inactivated SARS-CoV-2 vaccine, has been widely implemented in combating the COVID-19 pandemic. We summarized the results of clinical trials and real-world studies of CoronaVac in this review. The overall efficacy for the prevention of symptomatic COVID-19 (before the emergence of variants of concern) using two doses of 3 μg CoronaVac was 67.7% (95% CI, 35.9% to 83.7%). Effectiveness in preventing hospitalizations, ICU admissions, and deaths was more prominent than that in preventing COVID-19. A third dose inherited the effectiveness against non-variants of concern and increased effectiveness against severe COVID-19 outcomes caused by omicron variants compared to two doses. Most adverse reactions were mild. Few vaccine-related serious adverse reactions have been reported. Moreover, three-dose regimen significantly increased the seroconversion levels of neutralizing antibodies against omicron as compared to two-dose regimen. This review of CoronaVac may provide a scientific basis for optimizing global immunization strategies.

Neutralizing antibodies induced by homologous and heterologous boosters in CoronaVac vaccines in Chile

OBJECTIVES

To determine the impact of a booster dose on the humoral response in individuals inoculated with a complete schedule of any SARS-CoV-2 vaccine, we evaluated the neutralizing antibody (NAb) titres of homologous or heterologous booster doses over a 90-days period in CoronaVac vaccinees from 3 centres in Santiago, Chile.

METHODS

Individuals previously inoculated with 2 doses of CoronaVac (N = 523) were recruited in the context of the REFUERZO clinical trial (NCT04992182) and received either placebo (N = 129), or a booster dose of CoronaVac (N = 134), BNT162b2 (N = 133), or ChAdOx1 (N = 127). Pseudovirus neutralizing antibody titres (pVNT) were determined at baseline (day 0) as well as at days 14, 30, 60, and 90 after booster dose administration.

RESULTS

Inoculating a booster dose increases the pVNTs titres at days 14 and 30 in all groups, (13.5- and 12.0-fold increase for the CoronaVac group; 247.0- and 212.3-fold increase for the BTN162b2 group; and 89.1- and 128.1-fold increase for ChAdOx1 at each time point, respectively) with a decline observed at days 60 and 90. However, although pVNTs remained significantly higher for the BTN162b2 and ChAdOx1 groups at days 60 and 90, NAb titres reached baseline levels in the CoronaVac group at 90 days after inoculation.

DISCUSSION

A single heterologous booster (BTN162b2 or ChAdOx1) in individuals who completed the CoronaVac primary series resulted in an important increase in NAb titres remaining significantly higher at least for 90 days. These data may directly impact middle- and low-income countries currently using CoronaVac as the main vaccination strategy.

Protection from infection or disease? Re-evaluating the broad immunogenicity of inactivated SARS-CoV-2 vaccines

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Viral lineages that escape antibodies have changed the landscape of the pandemic.

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SARS-CoV-2 specific T cells effectively protect against disease development.

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Vaccine efficacy should be evaluated by its ability to protect from severe disease.

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Inactivated SARS-CoV-2 vaccine induces a multi-protein specific T cell response.

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The superior breadth of the vaccine T cell response could be a protective asset.

The duration and breadth of antibody responses to 3-dose of inactivated COVID-19 vaccinations in healthy blood donors: An observational study

Objectives

We aimed to evaluate the duration and breadth of antibodies elicited by inactivated COVID-19 vaccinations in healthy blood donors.

Methods

We performed serological tests on 1,417 samples from 658 blood donors who received two (n=357), or three (n=301) doses of COVID-19 inactivated vaccine. We also accessed the change in antibody response before and after booster vaccination in 94 participants and their neutralization breadth to the current variants after the booster.

Results

Following vaccination, for either the 2- or 3-dose, the neutralizing antibodies (nAbs) peaked with about 97% seropositivity approximately within one month but subsequently decreased over time. Of plasmas collected 6-8 months after the last immunization, the nAb seropositivities were 37% and 85% in populations with 2-dose and 3-dose vaccinations, respectively. The nAbs of plasma samples (collected between 2-6 weeks after the 3rd dose) from triple-vaccinated donors (n=94) showed a geometric mean titer of 145.3 (95% CI: 117.2 to 180.1) against the ancestral B.1, slightly reduced by 1.7-fold against Delta variant, but markedly decreased by 4-6 fold in neutralizing Omicron variants, including the sub-lineages of BA.1 (5.6-fold), BA.1.1 (6.0-fold), BA.2 (4.2-fold), B.2.12.1 (6.2-fold) and BA.4/5 (6.5-fold).

Conclusion

These findings suggested that the 3rd dose of inactivated COVID-19 vaccine prolongs the antibody duration in healthy populations, but the elicited-nAbs are less efficient in neutralizing circulating Omicron variants.

Effectiveness of COVID-19 Vaccination on Reduction of Hospitalizations and Deaths in Elderly Patients in Rio Grande do Norte, Brazil

Since the COVID-19 pandemic emerged, vaccination has been the core strategy to mitigate the spread of SARS-CoV-2 in humans. This paper analyzes the impact of COVID-19 vaccination on hospitalizations and deaths in the state of Rio Grande do Norte, Brazil. We analyzed data from 23,516 hospitalized COVID-19 patients diagnosed between April 2020 and August 2021. We excluded the data from patients hospitalized through direct occupancy, unknown outcomes, and unconfirmed COVID-19 cases, resulting in data from 12,635 patients cross-referenced with the immunization status during hospitalization. Our results indicated that administering at least one dose of the immunizers was sufficient to significantly reduce the occurrence of moderate and severe COVID-19 cases among patients under 59 years. Considering the partially or fully immunized patients, the mean age is similar between the analyzed groups, despite the occurrence of comorbidities and higher than that observed among not immunized patients. Thus, immunized patients present lower Unified Score for Prioritization (USP) levels when diagnosed with COVID-19. Our data suggest that COVID-19 vaccination significantly reduced the hospitalization and death of elderly patients (60+ years) after administration of at least one dose. Comorbidities do not change the mean age of moderate/severe COVID-19 cases and the days required for the hospitalization of these patients.

Gam-COVID-Vac, EpiVacCorona, and CoviVac effectiveness against lung injury during Delta and Omicron variant surges in St. Petersburg, Russia: a test-negative case-control study

Background

Monitoring vaccine effectiveness (VE) remains a priority for epidemiological research throughout the COVID-19 pandemic. VE against infection declines with the emergence of new SARS-CoV-2 variants of concern (VOC), but VE against the severe disease remains high. Therefore, we aimed to estimate the effectiveness of COVID-19 vaccines used in Russia against lung injury during Delta and Omicron VOC surges.

Methods

We designed a case–control study (test-negative design) to estimate VE against any (any volume of involved lung parenchyma) and severe (>50% of involved parenchyma) lung injury detected on computer tomography and associated with COVID-19 between October 1, 2021–April 28, 2022 (Delta VOC dominance period followed by Omicron dominance period). We included the data of patients with symptomatic confirmed SARS-CoV-2 infection referred to the low-dose computer tomography triage centres.

Results

Among 23996 patients in the primary analysis, 13372 (55.7%) had any lung injury, and 338 (1.4%) had severe lung injury. The adjusted for age, sex and triage centre VE estimates against any lung injury were 56% (95% confidence interval 54–59) for two-dose Gam-COVID-Vac (Sputnik V), 71% (68–74) for three-dose Gam-COVID-Vac (booster), 2% (−27 to 24) for EpiVacCorona, and 46% (37–53) for CoviVac. VE estimates against severe lung injury were 76% (67–82) for two-dose Gam-COVID-Vac (Sputnik V), 87% (76–93) for three-dose Gam-COVID-Vac, 36% (−63 to 75) for EpiVacCorona, and 80% (45–92) for CoviVac.

Conclusions

Gam-COVID-Vac remained effective against lung injury associated with COVID-19 during Delta and Omicron VOC surges, and one Gam-COVID-Vac booster could be seen as an appropriate option after a two-dose regimen. CoviVac was also effective against lung injury. EpiVacCorona use in population-based vaccination should be halted until effectiveness and efficacy evidence is provided.

Trial registration The joint study of COVID-19 vaccine effectiveness in St. Petersburg was registered at ClinicalTrials.gov (NCT04981405, date of registration—August 4, 2021).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02206-3.

Effectiveness of an inactivated Covid-19 vaccine with homologous and heterologous boosters against Omicron in Brazil

The effectiveness of inactivated vaccines (VE) against symptomatic and severe COVID-19 caused by omicron is unknown. We conducted a nationwide, test-negative, case-control study to estimate VE for homologous and heterologous (BNT162b2) booster doses in adults who received two doses of CoronaVac in Brazil in the Omicron context. Analyzing 1,386,544 matched-pairs, VE against symptomatic disease was 8.6% (95% CI, 5.6-11.5) and 56.8% (95% CI, 56.3-57.3) in the period 8-59 days after receiving a homologous and heterologous booster, respectively. During the same interval, VE against severe Covid-19 was 73.6% (95% CI, 63.9-80.7) and 86.0% (95% CI, 84.5-87.4) after receiving a homologous and heterologous booster, respectively. Waning against severe Covid-19 after 120 days was only observed after a homologous booster. Heterologous booster might be preferable to individuals with completed primary series inactivated vaccine.

Effectiveness of CoronaVac vaccination against COVID-19 development in healthcare workers: real-life data

Background: This study was designed to investigate the effectiveness of CoronaVac in preventing COVID-19 in healthcare workers (HCWs) during the Alpha variant-dominant period. Materials & methods: Follow-up was initiated 14 days after the second dose for double-dose vaccinated HCWs and on 25 February 2021, for the unvaccinated group. The incidence rate ratio was calculated to estimate the unadjusted effectiveness. Cox regression was used to adjust the effectiveness of CoronaVac. Results & Conclusion: The adjusted effectiveness of CoronaVac against COVID-19 was 65% (95% CI: 50-75%). Compared with the results of the phase III trial conducted in Turkey, a lower effectiveness of CoronaVac against COVID-19 was detected in this real-life study. This finding suggests that mass vaccination and booster doses are needed.

Estimating conditional vaccine effectiveness

Vaccine effectiveness for COVID-19 is typically estimated for different outcomes that often are hierarchical in severity (e.g. any documented infection, symptomatic infection, hospitalization, death) and subsets of each other. Conditional effectiveness for a more severe outcome conditional on a less severe outcome is the protection offered against the severe outcome (e.g. death) among those who already sustained the less severe outcome (e.g. documented infection). The concept applies also to the protection offered by previous infection rather than vaccination. Formulas and a nomogram are provided here for calculating conditional effectiveness. Illustrative examples are presented from recent vaccine effectiveness studies, including situations where effectiveness for different outcomes changed at different pace over time. E(death | documented infection) is the percent decrease in the case fatality rate and E(death | infection) is the percent decrease in the infection fatality rate (IFR). Conditional effectiveness depends on many factors and should not be misinterpreted as a causal effect estimate. However, it may be used for better personalized communication of the benefits of vaccination, considering also IFR and epidemic activity in public health decision-making and communication.