Waning COVID-19 Vaccine Effectiveness for BNT162b2 and CoronaVac in Malaysia: An Observational Study

Assessing the dynamics and impact of COVID-19 vaccination on disease spread: A data-driven approach

The COVID-19 pandemic has significantly impacted global health, social, and economic situations since its emergence in December 2019. The primary focus of this study is to propose a distinct vaccination policy and assess its impact on controlling COVID-19 transmission in Malaysia using a Bayesian data-driven approach, concentrating on the year 2021. We employ a compartmental Susceptible-Exposed-Infected-Recovered-Vaccinated (SEIRV) model, incorporating a time-varying transmission rate and a data-driven method for its estimation through an Exploratory Data Analysis (EDA) approach. While no vaccine guarantees total immunity against the disease, and vaccine immunity wanes over time, it is critical to include and accurately estimate vaccine efficacy, as well as a constant vaccine immunity decay or wane factor, to better simulate the dynamics of vaccine-induced protection over time. Based on the distribution and effectiveness of vaccines, we integrated a data-driven estimation of vaccine efficacy, calculated at 75% for Malaysia, underscoring the model's realism and relevance to the specific context of the country. The Bayesian inference framework is used to assimilate various data sources and account for underlying uncertainties in model parameters. The model is fitted to real-world data from Malaysia to analyze disease spread trends and evaluate the effectiveness of our proposed vaccination policy. Our findings reveal that this distinct vaccination policy, which emphasizes an accelerated vaccination rate during the initial stages of the program, is highly effective in mitigating the spread of COVID-19 and substantially reducing the pandemic peak and new infections. The study found that vaccinating 57-66% of the population (as opposed to 76% in the real data) with a better vaccination policy such as proposed here is able to significantly reduce the number of new infections and ultimately reduce the costs associated with new infections. The study contributes to the development of a robust and informative representation of COVID-19 transmission and vaccination, offering valuable insights for policymakers on the potential benefits and limitations of different vaccination policies, particularly highlighting the importance of a well-planned and efficient vaccination rollout strategy. While the methodology used in this study is specifically applied to national data from Malaysia, its successful application to local regions within Malaysia, such as Selangor and Johor, indicates its adaptability and potential for broader application. This demonstrates the model's adaptability for policy assessment and improvement across various demographic and epidemiological landscapes, implying its usefulness for similar datasets from various geographical regions.

Sero-epidemiological investigation and cross-neutralization activity against SARS-CoV-2 variants in cats and dogs, Thailand

Epidemiological data on SARS-CoV-2 infection in companion animals have been thoroughly investigated in many countries. However, information on the neutralizing cross-reactivity against SARS-CoV-2 variants in companion animals is still limited. Here, we explored the neutralizing antibodies against SARS-CoV-2 in cats and dogs between May 2020 and December 2021 during the first wave (a Wuhan-Hu-1-dominant period) and the fourth wave (a Delta-dominant period) of the Thailand COVID-19 outbreak. Archival plasma samples of 1,304 cats and 1,795 dogs (total = 3,099) submitted for diagnosis and health checks were collected at the Prasu-Arthorn Veterinary Teaching Hospital, Faculty of Veterinary Science, Mahidol University, Nakhon Pathom. A microneutralization test was used to detect neutralizing antibodies against the ancestral Wuhan-Hu-1 and the Delta variants. A plasma sample with neutralizing titers ≥10 was considered positive. Our results showed relatively low seroprevalence with seropositive samples detected in 8 out of 3,099 individuals (0.26, 95% CI 0.11-0.51%). Among these cases, SARS-CoV-2 neutralizing antibodies from both the ancestral Wuhan-Hu-1 and the Delta variants were found in three out of eight cases in two cats (n = 2) and one dog (n = 1). Furthermore, neutralizing antibodies specific to only the ancestral Wuhan-Hu-1 variant were exclusively found in one cat (n = 1), while antibodies against only the Delta variant were detected in four dogs (n = 4). Additionally, the neutralizing cross-activities against SARS-CoV-2 variants (Alpha, Beta, and Omicron BA.2) were observed in the seropositive cats with limited capacity to neutralize the Omicron BA.2 variant. In summary, the seropositivity among cats and dogs in households with an unknown COVID-19 status was relatively low in Thailand. Moreover, the neutralizing antibodies against SARS-CoV-2 found in the seropositive cats and dogs had limited or no ability to neutralize the Omicron BA.2 variant. Thus, monitoring SARS-CoV-2 infection and sero-surveillance, particularly in cats, is imperative for tracking virus susceptibility to the emergence of new SARS-CoV-2 variants.

Clinical outcomes and risk factors for SARS-CoV-2 breakthrough cases following vaccination with BNT162b2, CoronaVac, or ChAdOx1-S: A retrospective cohort study in Malaysia

Background

The SARS-CoV-2 pandemic drove global vaccination. However, breakthrough infections raised concerns about vaccine performance, leading the World Health Organization (WHO) to recommend investigations thereof. This study aimed to evaluate the clinical outcomes (time to breakthrough infection, intensive care unit [ICU] admission, and in-hospital mortality) of hospitalised patients with SARS-CoV-2 breakthrough infection. This was the primary outcome and the risk factors associated with its severity were the secondary outcomes.

Methods

This retrospective cohort study at a multispecialty tertiary hospital in Selangor, Malaysia included 200 fully adult vaccinated patients, with confirmed SARS-CoV-2 infection, admitted from September 2021 to February 2022. Participants were selected by simple random sampling. Infection severity was categorised as CAT 2-3 (mild-moderate) and 4-5 (severe-critical).

Results

The time to breakthrough infection was significantly longer for BNT162B2 recipients (128.47 ± 46.21 days) compared to CoronaVac (94.09 ± 48.71 days; P = 0.001) and ChAdOx1-S recipients (90.80 ± 37.59 days; P = 0.019). No significant associations were found between SARS-CoV-2-related ICU admission, mortality, and the vaccines. Multivariable analysis identified vaccine type, variant of concern, ethnicity, and hypertension as significant predictors of severity. BNT162b2 and ChAdOx1-S recipients had significantly (81 % and 74 %, respectively) lower odds of CAT 4-5 infection compared to CoronaVac recipients. Indian patients had a significantly (83 %) lower chance of CAT 4-5 infection compared to Malay patients. Patients with breakthrough infections during the Omicron period had a significantly (58 %) lower risk of CAT 4-5 compared to those in the Delta period. The CAT 4-5 risk was significantly (nearly threefold) higher in hypertensive patients.

Conclusion

The results support the Malaysian Ministry of Health's recommended booster three months after primary vaccination and the WHO's recommended heterologous booster following CoronaVac. Certain ethnic groups, hypertensive patients, and viral variants may require attention in future pandemics.

Association between Gut Microbiota Composition and Long-Term Vaccine Immunogenicity following Three Doses of CoronaVac

BACKGROUND

Neutralizing antibody level wanes with time after COVID-19 vaccination. We aimed to study the relationship between baseline gut microbiota and immunogenicity after three doses of CoronaVac.

METHODS

This was a prospective cohort study recruiting three-dose CoronaVac recipients from two centers in Hong Kong. Blood samples were collected at baseline and one year post-first dose for virus microneutralization (vMN) assays to determine neutralization titers. The primary outcome was high immune response (defined as with vMN titer ≥ 40). Shotgun DNA metagenomic sequencing of baseline fecal samples identified potential bacterial species and metabolic pathways using Linear Discriminant Analysis Effect Size (LEfSe) analysis. Univariate and multivariable logistic regression models were used to identify high response predictors.

RESULTS

In total, 36 subjects were recruited (median age: 52.7 years [IQR: 47.9-56.4]; male: 14 [38.9%]), and 18 had low immune response at one year post-first dose vaccination. Eubacterium rectale (log10LDA score = 4.15, p = 0.001; relative abundance of 1.4% vs. 0, p = 0.002), Collinsella aerofaciens (log10LDA score = 3.31, p = 0.037; 0.39% vs. 0.18%, p = 0.038), and Streptococcus salivarius (log10LDA score = 2.79, p = 0.021; 0.05% vs. 0.02%, p = 0.022) were enriched in low responders. The aOR of high immune response with E. rectale, C. aerofaciens, and S. salivarius was 0.03 (95% CI: 9.56 × 10-4-0.32), 0.03 (95% CI: 4.47 × 10-4-0.59), and 10.19 (95% CI: 0.81-323.88), respectively. S. salivarius had a positive correlation with pathways enriched in high responders like incomplete reductive TCA cycle (log10LDA score = 2.23). C. aerofaciens similarly correlated with amino acid biosynthesis-related pathways. These pathways all showed anti-inflammation functions.

CONCLUSION

E. rectale,C. aerofaciens, and S. salivarius correlated with poorer long-term immunogenicity following three doses of CoronaVac.

Predicting COVID-19 Re-Positive Cases in Malnourished Older Adults: A Clinical Model Development and Validation

Purpose

Building and validating a clinical prediction model for novel coronavirus (COVID-19) re-positive cases in malnourished older adults.

Patients and Methods

Malnourished older adults from January to May 2023 were retrospectively collected from the Department of Geriatrics of the Affiliated Hospital of Chengdu University of Traditional Chinese Medicine. They were divided into a "non-re-positive" group and a "re-positive" group based on the number of COVID-19 infections, and into a training set and a validation set at a 7:3 ratio. The least absolute shrinkage and selection operator (LASSO) regression analysis was used to identify predictive factors for COVID-19 re-positivity in malnourished older adults, and a nomogram was constructed. Independent influencing factors were screened by multivariate logistic regression. The model's goodness-of-fit, discrimination, calibration, and clinical impact were assessed by Hosmer-Lemeshow test, area under the curve (AUC), calibration curve, decision curve analysis (DCA), and clinical impact curve analysis (CIC), respectively.

Results

We included 347 cases, 243 in the training set, and 104 in the validation set. We screened 10 variables as factors influencing the outcome. By multivariate logistic regression analysis, preliminary identified protective factors, risk factors, and independent influencing factors that affect the re-positive outcome. We constructed a clinical prediction model for COVID-19 re-positivity in malnourished older adults. The Hosmer-Lemeshow test yielded χ2 =5.916, P =0.657; the AUC was 0.881; when the threshold probability was >8%, using this model to predict whether malnourished older adults were re-positive for COVID-19 was more beneficial than implementing intervention programs for all patients; when the threshold was >80%, the positive estimated value was closer to the actual number of cases.

Conclusion

This model can help identify the risk of COVID-19 re-positivity in malnourished older adults early, facilitate early clinical decision-making and intervention, and have important implications for improving patient outcomes. We also expect more large-scale, multicenter studies to further validate, refine, and update this model.

Immunogenicity and safety of RAZI recombinant spike protein vaccine (RCP) as a booster dose after priming with BBIBP-CorV: a parallel two groups, randomized, double blind trial

BACKGROUND

The immunity induced by primary vaccination is effective against COVID-19; however, booster vaccines are needed to maintain vaccine-induced immunity and improve protection against emerging variants. Heterologous boosting is believed to result in more robust immune responses. This study investigated the safety and immunogenicity of the Razi Cov Pars vaccine (RCP) as a heterologous booster dose in people primed with Beijing Bio-Institute of Biological Products Coronavirus Vaccine (BBIBP-CorV).

METHODS

We conducted a randomized, double-blind, active-controlled trial in adults aged 18 and over primarily vaccinated with BBIBP-CorV, an inactivated SARS-CoV-2 vaccine. Eligible participants were randomly assigned (1:1) to receive a booster dose of RCP or BBIBP-CorV vaccines. The primary outcome was neutralizing antibody activity measured by a conventional virus neutralization test (cVNT). The secondary efficacy outcomes included specific IgG antibodies against SARS-CoV-2 spike (S1 and receptor-binding domain, RBD) antigens and cell-mediated immunity. We measured humoral antibody responses at 2 weeks (in all participants) and 3 and 6 months (a subgroup of 101 participants) after the booster dose injection. The secondary safety outcomes were solicited and unsolicited immediate, local, and systemic adverse reactions.

RESULTS

We recruited 483 eligible participants between December 7, 2021, and January 13, 2022. The mean age was 51.9 years, and 68.1% were men. Neutralizing antibody titers increased about 3 (geometric mean fold increase, GMFI = 2.77, 95% CI 2.26-3.39) and 21 (GMFI = 21.51, 95% CI 16.35-28.32) times compared to the baseline in the BBIBP-CorV and the RCP vaccine groups. Geometric mean ratios (GMR) and 95% CI for serum neutralizing antibody titers for RCP compared with BBIBP-CorV on days 14, 90, and 180 were 6.81 (5.32-8.72), 1.77 (1.15-2.72), and 2.37 (1.62-3.47) respectively. We observed a similar pattern for specific antibody responses against S1 and RBD. We detected a rise in gamma interferon (IFN-γ), tumor necrosis factor (TNF-α), and interleukin 2 (IL-2) following stimulation with S antigen, particularly in the RCP group, and the flow cytometry examination showed an increase in the percentage of CD3 + /CD8 + lymphocytes. RCP and BBIBP-CorV had similar safety profiles; we identified no vaccine-related or unrelated deaths.

CONCLUSIONS

BBIBP-CorV and RCP vaccines as booster doses are safe and provide a strong immune response that is more robust when the RCP vaccine is used. Heterologous vaccines are preferred as booster doses.

TRIAL REGISTRATION

This study was registered with the Iranian Registry of Clinical Trial at www.irct.ir , IRCT20201214049709N4. Registered 29 November 2021.

Effectiveness of vero cell inactivated vaccine against severe acute respiratory infections (SARI) in Sibu, Malaysia: A retrospective test-negative design

The effectiveness of the vero cell inactivated vaccine (CoronaVac®) against severe acute respiratory infection (‎SARI)‎ caused by SARS-CoV-2 in the real world was assessed. A matched test-negative case-control design was employed using the web-based national information system, as well as the hospitalization dataset in Sibu Hospital. Vaccine effectiveness was measured by conditional logistic regression with adjustment for gender, underlying comorbidity, smoking status, and education level. Between 15 March and 30 September 2021, 838 eligible SARI patients were identified from the hospitalization records. Vaccine effectiveness was 42.4% (95% confidence interval [CI]: -28.3 to 74.1) for partial vaccination (after receiving the first dose to 14 days after receiving the second dose), and 76.5% (95% CI: 45.6 to 89.8) for complete vaccination (at 15 days or more after receiving the second dose). This analysis indicated that two doses of CoronaVac® vaccine provided efficacious protection against SARI caused by SARS-CoV-2 in the short term. However, the duration of protection, and performance against new variants need to be studied continuously.

Climate-dependent effectiveness of nonpharmaceutical interventions on COVID-19 mitigation

Environmental factors have a significant impact on the transmission of infectious diseases. Existing results show that the novel coronavirus can persist outside the host. We propose a susceptible-exposed-presymptomatic-infectious-asymptomatic-recovered-susceptible (SEPIARS) model with a vaccination compartment and indirect incidence to explore the effect of environmental conditions, temperature and humidity, on the transmission of the SARS-CoV-2 virus. Using climate data and daily confirmed cases data in two Canadian cities with different atmospheric conditions, we evaluate the mortality rates of the SARS-CoV-2 virus and further estimate the transmission rates by the inverse method, respectively. The numerical results show that high temperature or humidity can be helpful in mitigating the spread of COVID-19 during the warm summer months. Our findings verify that nonpharmaceutical interventions are less effective if the virus can persist for a long time on surfaces. Based on climate data, we can forecast the transmission rate and the infection cases up to four weeks in the future by a generalized boosting machine learning model.

Heterologous booster vaccines reduce severity and mortality in COVID-19 during BA.2 and BA.4/BA.5 omicron predominance in Thailand

BACKGROUND

The COVID-19 pandemic has evolved quickly, with variants of concern resulting in the need to offer booster vaccinations. Unfortunately, the booster uptake has been slow and vaccine response has shown to wane over time. Therefore, it's critical to evaluate the role of vaccinations on outcomes with newer sub-lineages of omicron.

METHODS

Utilising a Hospital Information System established in Chiang Mai, Thailand, we conducted a cohort study by linking patient-level data of laboratory-confirmed COVID-19 cases to the national immunization records, during BA.2 and BA.4/BA.5 predominance.

RESULTS

In adjusted cox-proportional hazard models, BA.4/BA.5 was not associated with more severe COVID-19 outcomes or deaths as compared to BA.2. Risk of severe outcomes and deaths were significantly reduced with third (87% and 95%) and fourth (88% and 95%) dose vaccination, while events were not observed with a fifth dose. Across the regimens, vaccination within 14-90 days prior showed the highest level of protection. All the vaccine types used for boosting in Thailand offered similar protection against severe COVID-19.

CONCLUSIONS

Boosters provide high level of protection against severe COVID-19 outcomes and deaths with newer omicron sub-lineages. Booster campaigns should focus on improving coverage utilising all available vaccines to ensure optimal protection.

Waning of SARS-CoV-2 Vaccine Effectiveness in COPD Patients: Lessons from the Delta Variant

Although the COVID-19 pandemic is profoundly changing, data on the effect of vaccination and duration of protection against infection and severe disease can still be advantageous, especially for patients with COPD, who are more vulnerable to respiratory infections. The Hungarian COVID-19 registry was retrospectively investigated for risk of infection and hospitalization by time since the last vaccination, and vaccine effectiveness (VE) was calculated in adults with COPD diagnosis and an exact-matched control group during the Delta variant of concern (VOC) wave in Hungary (September-December 2021). For the matching, sex, age, major co-morbidities, vaccination status, and prior infection data were obtained on 23 August 2021. The study population included 373,962 cases divided into COPD patients (age: 66.67 ± 12.66) and a 1:1 matched group (age: 66.73 ± 12.67). In both groups, the female/male ratio was 52.2:47.7, respectively. Among the unvaccinated, there was no difference between groups in risk for infection or hospitalization. Regarding vaccinated cases, in the COPD group, a slightly faster decline in effectiveness was noted for hospitalization prevention, although in both groups, the vaccine lost its significant effect between 215 and 240 days after the last dose of vaccination. Based on a time-stratified multivariate Cox analysis of the vaccinated cases, the hazard was constantly higher in the COPD group, with an HR of 1.09 (95%: 1.05-1.14) for infection and 1.87 (95% CI: 1.59-2.19) for hospitalization. In our study, COPD patients displayed lower vaccine effectiveness against SARS-CoV-2 infection and hospitalization but a similar waning trajectory, as vaccines lost their preventive effect after 215 days. These data emphasize revaccination measures in the COPD patient population.

Vaccine efficacy against SARS-CoV-2 for Pfizer BioNTech, Moderna, and AstraZeneca vaccines: a systematic review

The purpose of this systematic review was to report on the vaccine efficacy (VE) of three SARS-CoV-2 vaccines approved by Health Canada: Pfizer BioNTech, Moderna, and AstraZeneca. Four databases were searched for primary publications on population-level VE. Ninety-two publications matched the inclusion criteria, and the extracted data were separated by vaccine type: mRNA vaccines (Pfizer and Moderna) and the AstraZeneca vaccine. The median VE for PCR-positive patients and various levels of clinical disease was determined for the first and second doses of both vaccine types against multiple SARS-CoV-2 variants. The median VE for PCR-positive infections against unidentified variants from an mRNA vaccine was 64.5 and 89%, respectively, after one or two doses. The median VE for PCR-positive infections against unidentified variants from the AstraZeneca vaccine was 53.4 and 69.6%, respectively, after one or two doses. The median VE for two doses of mRNA for asymptomatic, symptomatic, and severe infection against unidentified variants was 85.5, 93.2, and 92.2%, respectively. The median VE for two doses of AstraZeneca for asymptomatic, symptomatic, and severe infection against unidentified variants was 69.7, 71, and 90.2%, respectively. Vaccine efficacy numerically increased from the first to the second dose, increased from the first 2 weeks to the second 2 weeks post-vaccination for both doses, but decreased after 4 months from the second dose. Vaccine efficacy did not differ by person's age.

Forecasting the effects of vaccination on the COVID-19 pandemic in Malaysia using SEIRV compartmental models

OBJECTIVES

This study aimed to develop susceptible-exposed-infectious-recovered-vaccinated (SEIRV) models to examine the effects of vaccination on coronavirus disease 2019 (COVID-19) case trends in Malaysia during Phase 3 of the National COVID-19 Immunization Program amidst the Delta outbreak.

METHODS

SEIRV models were developed and validated using COVID-19 case and vaccination data from the Ministry of Health, Malaysia, from June 21, 2021 to July 21, 2021 to generate forecasts of COVID-19 cases from July 22, 2021 to December 31, 2021. Three scenarios were examined to measure the effects of vaccination on COVID-19 case trends. Scenarios 1 and 2 represented the trends taking into account the earliest and latest possible times of achieving full vaccination for 80% of the adult population by October 31, 2021 and December 31, 2021, respectively. Scenario 3 described a scenario without vaccination for comparison.

RESULTS

In scenario 1, forecasted cases peaked on August 28, 2021, which was close to the peak of observed cases on August 26, 2021. The observed peak was 20.27% higher than in scenario 1 and 10.37% lower than in scenario 2. The cumulative observed cases from July 22, 2021 to December 31, 2021 were 13.29% higher than in scenario 1 and 55.19% lower than in scenario 2. The daily COVID-19 case trends closely mirrored the forecast of COVID-19 cases in scenario 1 (best-case scenario).

CONCLUSIONS

Our study demonstrated that COVID-19 vaccination reduced COVID-19 case trends during the Delta outbreak. The compartmental models developed assisted in the management and control of the COVID-19 pandemic in Malaysia.

The effectiveness of primary series CoronaVac vaccine in preventing COVID-19 illness: A prospective cohort study among healthcare workers in Azerbaijan, May-November 2021

Background

Healthcare workers (HCWs) have suffered considerable morbidity and mortality during the COVID-19 pandemic. Few studies have evaluated the CoronaVac vaccine effectiveness (VE), particularly in Eastern Europe, where the vaccine has been widely used.

Methods

We conducted a prospective cohort study among HCWs in seven hospitals in Baku, Azerbaijan between May 17 and November 30, 2021, to evaluate primary series (two-dose) CoronaVac VE against symptomatic SARS-CoV-2 infection. Participants completed weekly symptom questionnaires, provided nasopharyngeal swabs for SARS-CoV-2 RT-PCR testing when symptomatic, and provided serology samples at enrollment that were tested for anti-spike and anti-nucleocapsid antibodies. We estimated VE as (1 - hazard ratio)*100 using a Cox proportional hazards model with vaccination status as a time-varying exposure, adjusting for hospital and previous SARS-CoV-2 infection status.

Results

We enrolled 1582 HCWs. At enrollment, 1040 (66%) had received two doses of CoronaVac; 421 (27%) were unvaccinated. During the study period, 72 PCR-positive SARS-CoV-2 infections occurred; 36/39 (92%) sequenced samples were classified as Delta variants. Primary series VE against COVID-19 illness was 29% (95% CI: -51%; 67%) for the entire analysis period. For the Delta-only period (July 1-November 30, 2021), primary series VE was 19% (95% CI: -81%; 64%). For the entire analysis period, primary series VE was 39% (95% CI: -40%; 73%) for HCWs vaccinated within 14-149 days and 19% (95% CI: -81%; 63%) for those vaccinated ≥150 days.

Conclusions

During a period in Azerbaijan characterized by mostly Delta circulation, VE point estimates suggested that primary series CoronaVac protected nearly 1 in 3 HCWs against COVID-19, but 95% confidence intervals were wide, with lower bounds that crossed zero, reflecting the limited precision of our VE estimates. Our findings underscore the need to consider booster doses for individuals who have received the primary series of CoronaVac.

Assessing potential surge of COVID-19 cases and the need for booster vaccine amid emerging SARS-CoV-2 variants in Indonesia: A modelling study from West Java

Objectives

Primary and booster vaccinations are crucial in COVID-19 control. This study aimed to assess the minimum booster coverage to hamper potential surge of COVID-19 cases in 2023 in Indonesia, a low-resource setting country.

Methods

We used a modified SEIR compartment model to assess different scenarios in booster coverage across West Java population: 35%, 50%, and 70%. We fitted the model, then we calculated the potential active cases in 2023 if each scenario was met before 2022 ends. A heat map of predicted cases from various booster coverages and time frames was produced and matched with vaccination rate's function to determine feasible time frames.

Results

A minimum of 70% booster coverage in West Java is needed to reduce 90% of potential COVID-19 cases and avert possible surge in 2023. The booster doses should be distributed before February 2023 to achieve its optimum preventive effect. Delays in achieving minimum booster coverage is acceptable, but higher booster coverage will be required.

Conclusions

For better COVID-19 control in Indonesia, booster vaccination is warranted, as presented by a case study in West Java. Sufficient vaccine supplies, infrastructure, and healthcare workers should be ensured to support a successful booster vaccination program.

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 inactivated COVID-19 vaccines against SARS-CoV-2 infections among healthcare personnel in Pakistan: a test-negative case-control study

OBJECTIVE

During the COVID-19 pandemic, several vaccines that were efficacious in randomised controlled trials were authorised for mass vaccination. In developing countries, inactivated vaccines were widely administered. While inactivated vaccines have been deemed effective in reducing disease severity, for healthcare personnel (HCP), effectiveness against SARS-CoV-2 infections is essential to reduce the risk to vulnerable patients and ensure a stable healthcare workforce. There are limited studies examining inactivated vaccines' effectiveness against SARS-CoV-2 variants of concern (VOCs) in real-world settings. We estimated the effectiveness of inactivated vaccines (BBIBP-CorV and CoronaVac) against reverse transcription PCR (RT-PCR)-confirmed SARS-CoV-2 infections among HCP in the setting of emerging SARS-CoV-2 VOCs in Pakistan.

DESIGN

A retrospective matched, test-negative case-control analysis using existing data from an Employee Health database on HCP at a large, private healthcare system in Pakistan.

PARTICIPANTS

4599 HCP were tested between 1 April and 30 September 2021. Each case (PCR positive) was matched to two to six controls (PCR negative) by the date of the RT-PCR test (±7 days) to reduce bias.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome was vaccine effectiveness (VE) against SARS-CoV-2 infection. The secondary outcome was VE against symptomatic SARS-CoV-2 infection. Per cent VE was calculated using (1-OR)*100, with the OR of getting a PCR-confirmed SARS-COV-2 infection estimated using conditional logistic regression, after adjusting for age, gender, work area and history of SARS-CoV-2 infection.

RESULTS

Inactivated vaccines were ineffective against SARS-CoV-2 infections after receiving the first dose (VE 17%, 95% CI -10, 39; p=0.261). They showed modest effectiveness ≥14 days after the second dose against SARS-CoV-2 infections (VE 30%, 95% CI 7, 48; p=0.015) and symptomatic SARS-CoV-2 infections (VE 33%, 95% CI 6, 52; p=0.002).

CONCLUSIONS

Inactivated vaccines show modest effectiveness against SARS-CoV-2 infections in the setting of emerging VOCs. This builds a strong case for boosters and/or additional vaccination.

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.

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.

Heterogeneity in Vaccinal Immunity to SARS-CoV-2 Can Be Addressed by a Personalized Booster Strategy

SARS-CoV-2 vaccinations were initially shown to substantially reduce risk of severe disease and death. However, pharmacokinetic (PK) waning and rapid viral evolution degrade neutralizing antibody (nAb) binding titers, causing loss of vaccinal protection. Additionally, there is inter-individual heterogeneity in the strength and durability of the vaccinal nAb response. Here, we propose a personalized booster strategy as a potential solution to this problem. Our model-based approach incorporates inter-individual heterogeneity in nAb response to primary SARS-CoV-2 vaccination into a pharmacokinetic/pharmacodynamic (PK/PD) model to project population-level heterogeneity in vaccinal protection. We further examine the impact of evolutionary immune evasion on vaccinal protection over time based on variant fold reduction in nAb potency. Our findings suggest viral evolution will decrease the effectiveness of vaccinal protection against severe disease, especially for individuals with a less durable immune response. More frequent boosting may restore vaccinal protection for individuals with a weaker immune response. Our analysis shows that the ECLIA RBD binding assay strongly predicts neutralization of sequence-matched pseudoviruses. This may be a useful tool for rapidly assessing individual immune protection. Our work suggests vaccinal protection against severe disease is not assured and identifies a potential path forward for reducing risk to immunologically vulnerable individuals.

Vaccine effectiveness and duration of protection of COVID-19 mRNA vaccines against Delta and Omicron BA.1 symptomatic and severe COVID-19 outcomes in adults aged 50 years and over in France

The emergence of SARS-CoV-2 variants calls for continuous monitoring of vaccine effectiveness (VE). We estimated the absolute effectiveness of complete 2-dose primary vaccination and booster vaccination with COVID-19 mRNA vaccines, and the duration of protection against Delta and Omicron BA.1 symptomatic infection and severe outcomes. French residents aged ≥50 years, who presented with SARS-CoV-2-like symptoms and tested for SARS-CoV-2 between June 6, 2021 and February 10, 2022 were included. A test-negative study was conducted to estimate VE against symptomatic infection, using conditional logistic regression models. Cox proportional hazard regressions were performed to assess additional protection against severe COVID-19 outcomes (any hospitalization, and intensive care units [ICU] admission or in-hospital death). In total, 273732 cases and 735 919 controls were included. VE against symptomatic infection after 2-doses vaccination was 86% (95% CI: 75-92%) for Delta and 70% (58-79%) for Omicron, 7-30 days post vaccination. Protection waned over time, reaching 60% (57-63%) against Delta and 20% (16.-24%) for Omicron BA.1 > 120 days after vaccination. The booster dose fully restored protection against symtpomatic Delta infection (95% [81-99%]) but only partially against symptomatic Omicron BA.1 infection (63% [59-67%]). VE against Delta-related severe outcomes was above 95% with 2 doses, and persisted for at least four months. Protection against any Omicron BA.1-hospitalization was 92% (65%-99%) at 8-30 days, and 82% (67%-91%) > 120 days from the second dose. Against BA.1 ICU admission or in-patient death, VE stood at 98% (0-100%) at 8-30 days, and was 90% (40-99%) > 120 days from the second dose. Protection confered by mRNA vaccines against severe disease caused by either Delta or Omicron BA.1 appeared high and sustained over time. Protection against symptomatic diseases after 2 doses decreased rapidly, especially against Omicron BA.1. A booster dose restored high protection against Delta but only a partial one against Omicron BA.1.

Effectiveness of Inactivated Vaccine against SARS-CoV-2 Delta Variant Infection in Xiamen, China—A Test-Negative Case-Control Study

Objective: Vaccine effectiveness can measure herd immunity, but the effectiveness of inactivated vaccines in Xiamen remains unclear. Our study was designed to understand the herd immunity of the COVID-19 inactivated vaccine against the SARA-CoV-2 Delta variant in the real world of Xiamen. Methods: We carried out a test-negative case-control study to explore the vaccine’s effectiveness. Participants aged over 12 years were recruited. A logistic regression was used to estimate the odds ratio (OR) of the vaccine among cases and controls. Results: This outbreak began with factory transmission clusters, and spread to families and communities during the incubation period. Sixty percent of cases were confirmed in a quarantine site. A huge mass of confirmed cases (94.49%) was identified within three days, and nearly half of them had a low Ct value. Following an adjustment for age and sex, a single dose of inactivated SARS-CoV-2 vaccine yielded the vaccine effectiveness (VE) of the overall case, of 57.01% (95% CI: −91.44~86.39%), the fully VE was 65.72% (95% CI: −48.69~88.63%) against COVID-19, 59.45% against moderate COVID-19 and 38.48% against severe COVID-19, respectively. The VE of fully vaccinated individuals was significantly higher in females than in males (73.99% vs. 46.26%). The VE among participants aged 19~40 and 41~61 years was 78.75% and 66.33%, respectively, which exceeds the WHO’s minimal threshold. Nevertheless, the VE in people under 18 and over 60 years was not observed because of the small sample size. Conclusions: The single-dose vaccine had limited effectiveness in preventing infection of the Delta variant. The two doses of inactivated vaccine could effectively prevent infection, and clinical mild, moderate, and severe illness caused by the SARS-CoV-2 Delta variant in people aged 18–60 years in the real world.

COVID-19 endgame: From pandemic to endemic? Vaccination, reopening and evolution in low- and high-vaccinated populations

COVID-19 remains a major public health concern, with large resurgences even where there has been widespread uptake of vaccines. Waning immunity and the emergence of new variants will shape the long-term burden and dynamics of COVID-19. We explore the transition to the endemic state, and the endemic incidence in British Columbia (BC), Canada and South Africa (SA), to compare low and high vaccination coverage settings with differing public health policies, using a combination of modelling approaches. We compare reopening (relaxation of public health measures) gradually and rapidly as well as at different vaccination levels. We examine how the eventual endemic state depends on the duration of immunity, the rate of importations, the efficacy of vaccines and the transmissibility. These depend on the evolution of the virus, which continues to undergo selection. Slower reopening leads to a lower peak level of incidence and fewer overall infections in the wave following reopening: as much as a 60% lower peak and a 10% lower total in some illustrative simulations; under realistic parameters, reopening when 70% of the population is vaccinated leads to a large resurgence in cases. The long-term endemic behaviour may stabilize as late as January 2023, with further waves of high incidence occurring depending on the transmissibility of the prevalent variant, duration of immunity, and antigenic drift. We find that long term endemic levels are not necessarily lower than current pandemic levels: in a population of 100,000 with representative parameter settings (Reproduction number 5, 1-year duration of immunity, vaccine efficacy at 80% and importations at 3 cases per 100K per day) there are over 100 daily incident cases in the model. Predicted prevalence at endemicity has increased more than twofold after the emergence and spread of Omicron. The consequent burden on health care systems depends on the severity of infection in immunized or previously infected individuals.

An inactivated SARS-CoV-2 vaccine induced cross-neutralizing persisting antibodies and protected against challenge in small animals

Vaccines have relieved the public health burden of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and globally inactivated vaccines are most widely used. However, poor vaccination accessibility and waning immunity maintain the pandemic, driving emergence of variants. We developed an inactivated SARS-CoV-2 (I-SARS-CoV-2) vaccine based on a viral isolate with the Spike mutation D614G, produced in Vero cells in a scalable bioreactor, inactivated with β-propiolactone, purified by membrane-based steric exclusion chromatography, and adjuvanted with MF59-like adjuvant AddaVax. I-SARS-CoV-2 and a derived split vaccine induced persisting neutralizing antibodies in mice; moreover, lyophilized antigen was immunogenic. Following homologous challenge, I-SARS-CoV-2 immunized hamsters were protected against disease and lung pathology. In contrast with reports for widely used vaccines, hamster plasma similarly neutralized the homologous and the Delta (B.1.617.2) variant viruses, whereas the Omicron (B.1.1.529) variant was neutralized less efficiently. Applied bioprocessing approaches offer advantages regarding scalability and production, potentially benefitting worldwide vaccine coverage.

Real-world COVID-19 vaccine effectiveness against the Omicron BA.2 variant in a SARS-CoV-2 infection-naive population

The SARS-CoV-2 Omicron variant has demonstrated enhanced transmissibility and escape of vaccine-derived immunity. Although first-generation vaccines remain effective against severe disease and death, robust evidence on vaccine effectiveness (VE) against all Omicron infections, irrespective of symptoms, remains sparse. We used a community-wide serosurvey with 5,310 subjects to estimate how vaccination histories modulated risk of infection in infection-naive Hong Kong during a large wave of Omicron BA.2 epidemic in January-July 2022. We estimated that Omicron infected 45% (41-48%) of the local population. Three and four doses of BNT162b2 or CoronaVac were effective against Omicron infection 7 days after vaccination (VE of 48% (95% credible interval 34-64%) and 69% (46-98%) for three and four doses of BNT162b2, respectively; VE of 30% (1-66%) and 56% (6-97%) for three and four doses of CoronaVac, respectively). At 100 days after immunization, VE waned to 26% (7-41%) and 35% (10-71%) for three and four doses of BNT162b2, and to 6% (0-29%) and 11% (0-54%) for three and four doses of CoronaVac. The rapid waning of VE against infection conferred by first-generation vaccines and an increasingly complex viral evolutionary landscape highlight the necessity for rapidly deploying updated vaccines followed by vigilant monitoring of VE.

COVID-19 Vaccines-All You Want to Know

The severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) pandemic has led to an unprecedented public health crisis. The collective global response has led to production of multiple safe and effective vaccines utilizing novel platforms to combat the virus that have propelled the field of vaccinology forward. Significant challenges to universal vaccine effectiveness remain, including immune evasion by SARS-CoV-2 variants, waning of immune response, inadequate knowledge of correlates of protection, and dosing in special populations. This review serves as a detailed evaluation of the development of the current SARS-CoV-2 vaccines, their effectiveness, and challenges to their deployment as a preventive tool.

Estimation of Vaccine Effectiveness of CoronaVac and BNT162b2 Against Severe Outcomes Over Time Among Patients With SARS-CoV-2 Omicron

IMPORTANCE

Few studies have evaluated the waning of vaccine effectiveness against severe outcomes caused by SARS-CoV-2 Omicron infection. Hong Kong is providing inactivated and mRNA vaccines, but the population had limited protection from natural infections before the Omicron variant emerged.

OBJECTIVE

To examine the change in vaccine effectiveness against hospitalization and mortality due to the Omicron variant over time.

DESIGN, SETTING, AND PARTICIPANTS

This case-control study included adults with SARS-CoV-2 Omicron variant infection who died or were hospitalized in Hong Kong from January 1 to June 5, 2022 (ie, case participants), and adults with SARS-CoV-2 Omicron, sampled from the public health registry during the study period (ie, control participants), who were matched to case participants by propensity score.

EXPOSURES

Vaccination status of the individuals.

MAIN OUTCOMES AND MEASURES

Estimated vaccine effectiveness against death, death or hospitalization, and death among hospitalized patients. Vaccine effectiveness was calculated as 1 - adjusted odds ratio obtained by conditional logistic regression adjusted with covariates for each period following vaccination.

RESULTS

There were 32 823 case participants (25 546 [77.8%] ≥65 years; 16 930 [47.4%] female) and 131 328 control participants (100 041 [76.2%] ≥65 years; 66 625 [46.6%] female) in the sample analyzed for the death or hospitalization outcome. Vaccine effectiveness against death or hospitalization was maintained for at least 6 months after the second dose of both CoronaVac (74.0%; 95% CI, 71.8%-75.8%) and BNT162b2 (77.4%; 95% CI, 75.5%-79.0%) vaccines. Vaccine effectiveness against death in those aged 18 to 49 years was 86.4% (95% CI, 85.8%-87.0%) and 92.9% (95% CI, 92.6%-93.2%) for those receiving 2 doses of CoronaVac and BNT162b2, respectively, while for patients aged 80 years or older, it dropped to 61.4% (95% CI, 59.8%-63.2%) and 52.7% (95% CI, 50.2%-55.6%) for CoronaVac and BNT162b2, respectively. Nevertheless, overall vaccine effectiveness against death at 4 to 6 months after the third dose was greater than 90% for CoronaVac, BNT162b2, and the mixed vaccine schedule (eg, mixed vaccines: vaccine effectiveness, 92.2%; 95% CI, 89.2%-95.1%).

CONCLUSIONS AND RELEVANCE

While vaccines were generally estimated to be effective against severe outcomes caused by SARS-CoV-2 Omicron infection, this analysis found that protection in older patients was more likely to wane 6 months after the second dose. Hence, a booster dose is recommended for older patients to restore immunity. This is especially critical in a setting like Hong Kong, where third-dose coverage is still insufficient among older residents.

Effectiveness of Booster Vaccinations on the Control of COVID-19 during the Spread of Omicron Variant in Malaysia

(1) Background: The assessment of vaccine effectiveness against the Omicron variant is vital in the fight against COVID-19, but research on booster vaccine efficacy using nationwide data was lacking at the time of writing. This study investigates the effectiveness of booster doses on the Omicron wave in Malaysia against COVID-19 infections and deaths; (2) Methods: This study uses nationally representative data on COVID-19 from 1 January to 31 March 2022, when the Omicron variant was predominant in Malaysia. Daily new infections, deaths, ICU utilization and Rt values were compared. A screening method was used to predict the vaccine effectiveness against COVID-19 infections, whereas logistic regression was used to estimate vaccine effectiveness against COVID-19-related deaths, with efficacy comparison between AZD1222, BNT162b2 and CoronaVac; (3) Results: Malaysia's Omicron wave started at the end of January 2022, peaking on 5 March 2022. At the time of writing, statistics for daily new deaths, ICU utilization, and effective reproductive values (Rt) were showing a downtrend. Boosted vaccination is 95.4% (95% CI: 95.4, 95.4) effective in curbing COVID-19 infection, compared to non-boosted vaccination, which is 87.2% (95% CI: 87.2, 87.2). For symptomatic infection, boosted vaccination is 97.4% (95% CI: 97.4, 97.4) effective, and a non-boosted vaccination is 90.9% (95% CI: 90.9, 90.9). Against COVID-19-related death, boosted vaccination yields a vaccine effectiveness (VE) of 91.7 (95% CI: 90.6, 92.7) and full vaccination yields a VE of 65.7% (95% CI: 61.9, 69.1). Looking into the different vaccines as boosters, AZD1222 is 95.2% (CI 95%: 92.7, 96.8) effective, BNT162b2 is 91.8% (CI 95%: 90.7, 92.8) effective and CoronaVac is 88.8% (CI 95%: 84.9, 91.7) effective against COVID-19 deaths. (4) Conclusions: Boosters are effective in increasing protection against COVID-19, including the Omicron variant. Given that the VE observed was lower, CoronaVac recipients are encouraged to take boosters due to its lower VE.

Reduction in severity and mortality in COVID-19 patients owing to heterologous third and fourth-dose vaccines during the periods of delta and omicron predominance in Thailand

OBJECTIVES

The COVID-19 pandemic has evolved quickly, with different variants of concern resulting in the need for countries to offer booster vaccinations. Although studies have assessed homologous schedules in detail, the effectiveness of heterologous booster vaccine schedules against severity and mortality with newer variants remains to be explored fully.

METHODS

Utilizing a Hospital Information System for COVID-19 established in Chiang Mai, Thailand, we conducted a cohort study by linking patient-level data on laboratory-confirmed COVID-19 cases to the national immunization records, during delta-predominant and omicron-predominant periods.

RESULTS

Compared to omicron, COVID-19 cases during the delta period were 10 times more likely to have severe outcomes and in-hospital deaths. During omicron, a third vaccine dose had an 89% reduced risk of both severe COVID-19 and death. The third dose received 14-90 days before the date of the positive test showed the highest protection (93%). Severe outcomes were not observed with the third dose during delta, and the fourth dose during the omicron period. All the vaccine types used for boosting in Thailand offered similar protection against severe COVID-19.

CONCLUSION

Booster doses provided a very high level of protection against severe COVID-19 outcomes and deaths. Booster campaigns should focus on improving coverage by utilizing all available vaccines to ensure optimal protection.

Covid-19 vaccination reported side effects and hesitancy among the Syrian population: a cross-sectional study

INTRODUCTION

Studying post-vaccination side effects and identifying the reasons behind low vaccine uptake are pivotal for overcoming the pandemic.

METHODS

This cross-sectional study was distributed through social media platforms and face-to-face interviews. Data from vaccinated and unvaccinated participants were collected and analyzed using the chi-square test, multivariable logistic regression to detect factors associated with side effects and severe side effects.

RESULTS

Of the 3509 participants included, 1672(47.6%) were vaccinated. The most common reason for not taking the vaccine was concerns about the vaccine's side effects 815(44.4). The majority of symptoms were mild 788(47.1%), followed by moderate 374(22.3%), and severe 144(8.6%). The most common symptoms were tiredness 1028(61.5%), pain at the injection site 933(55.8%), and low-grade fever 684(40.9%). Multivariable logistic regression analysis revealed that <40 years (vs. ≥40; OR: 2.113, p-value = 0.008), females (vs. males; OR: 2.245, p-value< .001), did not receive influenza shot last year (vs. did receive Influenza shot last year OR: 1.697, p-value = 0.041), AstraZeneca (vs. other vaccine brands; OR: 2.799, p-value< .001), co-morbidities (vs. no co-morbidities; OR: 1.993, p-value = 0.008), and diabetes mellitus (vs. no diabetes mellitus; OR: 2.788, p-value = 0.007) were associated with severe post-vaccine side effects. Serious side effects reported were blood clots 5(0.3%), thrombocytopenia 2(0.1%), anaphylaxis 1(0.1%), seizures 1(0.1%), and cardiac infarction 1(0.1%).

CONCLUSION

Our study revealed that most side effects reported were mild in severity and self-limiting. Increasing the public's awareness of the nature of the vaccine's side effects would reduce the misinformation and improve the public's trust in vaccines. Larger studies to evaluate rare and serious adverse events and long-term side effects are needed, so people can have sufficient information and understanding before making an informed consent which is essential for vaccination.

Real-world effectiveness of homologous and heterologous BNT162b2, CoronaVac, and AZD1222 booster vaccination against Delta and Omicron SARS-CoV-2 infection

Given emerging evidence of immune escape in the SARS-CoV-2 Omicron viral variant, and its dominance, effectiveness of heterologous and homologous boosting schedules commonly used in low-to-middle income countries needs to be re-evaluated. We conducted a test-negative design using consolidated national administrative data in Malaysia to compare the effectiveness of homologous and heterologous BNT162b2, CoronaVac, and AZD1222 booster vaccination against SARS-CoV-2 infection in predominant-Delta and predominant-Omicron periods. Across both periods, homologous CoronaVac and AZD1222 boosting demonstrated lower effectiveness than heterologous boosting for CoronaVac and AZD1222 primary vaccination recipients and homologous BNT162b2 boosting. Broadly, marginal effectiveness was smaller by 40–50 percentage points in the Omicron period than the Delta period. Without effective and accessible second-generation vaccines, heterologous boosting using BNT162b2 for inactivated and vectored primary vaccination recipients is preferred.

Genomic Evidence Suggests Viral Persistence of SARS-CoV-2 for 386 Days in Health Worker: A Case Report from Santiago of Chile

The COVID-19 pandemic continues to affect several countries. One of the best ways to control its spread is the timely identification of infected patients for isolation and quarantine. While an episode of infection lasts an average of 8-10 days from the onset of symptoms, there is literature describing long-lasting viral persistence events. Here, we report a case of persistence of SARS-CoV-2 for 386 days in a health worker from Santiago de Chile. Our study could be one of the longest reported viral persistence events. RNA sequencing analyses indicated that the first positive diagnosis (8 June 2020) corresponded to a SARS-CoV-2 variant belonging to Clade Nextstrain 20A. Three hundred eighty-six days later (23 September 2021), the second positive result reached the same viral variant (Clade 20A) but without presence or circulation in Chile since May 2021. Both sequencing coverages showed an identity of 99.21%, with some mutations related to the severity of the disease (ORF1b:P314L) and more infectivity (S:D614G). This work reinforces the idea of implementing an RT-qPCR or rapid antigen test once the quarantine is fulfilled to ensure viral absence, identify potential persistence, and, consequently, minimize the risk of local outbreaks of SARS-CoV-2 infection.

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.

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.

Assessment of Heterologous and Homologous Boosting With Inactivated COVID-19 Vaccine at 3 Months Compared With Homologous Boosting of BNT162b2 at 6 Months

IMPORTANCE

Evidence for the timing of booster vaccination after completion of BNT162b2 and CoronaVac primary vaccination is crucial to guide policy recommendations.

OBJECTIVE

To compare the odds of symptomatic SARS-CoV-2 infection and COVID-19-related outcomes after heterologous and homologous boosting of CoronaVac at 3-month intervals and homologous boosting of BNT162b2 at 6-month intervals, with BNT162b2 primary series (2 doses) as the reference group.

DESIGN, SETTING, AND PARTICIPANTS

This population-based retrospective cohort study used national data for Malaysia. Participants included all individuals aged 18 years and older who received a complete primary series of CoronaVac or BNT162b2 vaccine and were eligible for a booster dose between November 21, 2021, and December 28, 2021. Data were analyzed from November 21, 2021, to January 7, 2022.

EXPOSURES

Receipt of a booster vs no booster and categorized into primary series BNT162b2 (2 doses of BNT162b2), primary series CoronaVac (2 doses of CoronaVac), 3 doses of BNT162b2, primary series CoronaVac plus a BNT162b2 booster, and 3 doses of CoronaVac.

MAIN OUTCOMES AND MEASURES

The primary outcome was symptomatic SARS-CoV-2 infection. The secondary outcomes were COVID-19-related intensive care unit admission and death. All outcomes were observed from the day an individual was considered fully boosted (≥14 days after booster dose).

RESULTS

Our cohort included 13 840 240 individuals (mean [SD] age, 39.9 [15.5] years; 7 040 298 [50.9%] men; 4 451 180 individuals [32.2%] with ≥1 comorbidities), of whom 5 081 641 individuals (36.7%) had received a booster dose. Using the primary series BNT162b2 recipients as reference, the adjusted odds against symptomatic SAR-CoV-2 infection were lower for individuals who received the primary series CoronaVac plus a BNT162b2 (adjusted odds ratio [aOR], 0.06 [95% CI, 0.05-0.06]), 3 doses of CoronaVac (aOR, 0.08 [95% CI, 0.06-0.10]), or 3 doses of BNT162b2 (aOR, 0.01 [95% CI, 0.00-0.01]). Receipt of heterologous booster (primary series of CoronaVac plus a BNT162b2 booster) was associated with lower odds of SARS-CoV-2 infection (aOR, 0.17 [95% CI, 0.17-0.18]) compared with homologous booster (3 doses of CoronaVac) for individuals aged 60 years and older (aOR, 0.19 [95% CI, 0.19-0.20]).

CONCLUSIONS AND RELEVANCE

In this cohort study, for individuals who received the CoronaVac primary series and a booster dose of BNT162b2 or CoronaVac at 3 months, the observed odds of symptomatic SARS-CoV-2 infection were similar to individuals who received the BNT162b2 primary series plus a third dose of BNT162b2 at 6 months. Heterologous booster is recommended for individuals aged 60 years or older who received the CoronaVac primary series, given the lower observed odds against symptomatic SARS-CoV-2 infection among those who received a BNT1612b2 booster.

Vaccine effectiveness of one, two, and three doses of BNT162b2 and CoronaVac against COVID-19 in Hong Kong: a population-based observational study

Background

Hong Kong maintained low circulation of SARS-CoV-2 until a major community epidemic of the omicron (B.1.1.529) sublineage BA.2 began in January, 2022. Both mRNA (BNT162b2 [Fosun Pharma-BioNTech]) and inactivated CoronaVac (Sinovac, Beijing, China) vaccines are widely available; however, vaccination coverage has been low, particularly in older adults aged 70 years or older. We aimed to assess vaccine effectiveness in this predominantly infection-naive population.

Methods

In this observational study, we used individual-level case data on mild or moderate, severe or fatal, and fatal disease in patients hospitalised with COVID-19 along with census information and coverage data of BNT162b2 and CoronaVac. We used a negative binomial model, adjusting for age, sex, and calendar day to estimate vaccine effectiveness of one, two, and three doses of both BNT162b2 and CoronaVac vaccines, and relative effectiveness by number of doses and vaccine type.

Findings

Between Dec 31, 2020, and March 16, 2022, 13·2 million vaccine doses were administered in Hong Kong's 7·4-million population. We analysed data from confirmed cases with mild or moderate (n=5566), severe or fatal (n=8875), and fatal (n=6866) COVID-19. Two doses of either vaccine protected against severe disease and death within 28 days of a positive test, with higher effectiveness among adults aged 60 years or older with BNT162b2 (vaccine effectiveness 89·3% [95% CI 86·6–91·6]) compared with CoronaVac (69·9% [64·4–74·6]). Three doses of either vaccine offered very high levels of protection against severe or fatal outcomes (97·9% [97·3–98·4]).

Interpretation

Third doses of either BNT162b2 or CoronaVac provide substantial additional protection against severe COVID-19 and should be prioritised, particularly in older adults older than 60 years and others in high-risk populations who received CoronaVac primary schedules. Longer follow-up is needed to assess duration of protection across different vaccine platforms and schedules.

Funding

COVID-19 Vaccines Evaluation Program, Chinese Center for Disease Control and Prevention.

Expert Review on global real-world vaccine effectiveness against SARS-CoV-2

INTRODUCTION

COVID-19 vaccines have been highly effective in reducing morbidity and mortality during the pandemic. While primary series vaccination rates are generally high in Southeast Asian (SEA) countries, various factors have limited the rollout and impact of booster doses.

AREAS COVERED

We reviewed 79 studies in the publicly available International Vaccine Access Center (IVAC) VIEW-hub platform on vaccine effectiveness (VE) after primary immunizations with two-dose schedules. VE data were reported for SARS-CoV-2 infection, COVID-19-related hospitalizations and deaths, and stratified across variants of concern (VOC), age, study design and prior SARS-CoV-2 infection for mRNA vaccines (BNT162b2, mRNA-1273 and combinations of both), vector vaccines (AstraZeneca, AZD1222 "Vaxzevria") and inactivated virus vaccines (CoronaVac).

EXPERT OPINION

The most-studied COVID-19 vaccines provide consistently high (>90%) protection against serious clinical outcomes like hospitalizations and deaths, regardless of variant. Additionally, this protection appears equivalent for mRNA vaccines and vector vaccines like AZD1222, as supported by our analysis of local Asian and relevant international data, and by insights from SEA experts. Given the continued impact of COVID-19 hospitalizations and deaths on healthcare systems worldwide, encouraging vaccination strategies that can reduce this burden is more relevant than attempting to prevent broader but milder infections with specific variants, including Omicron.

Change in covid-19 risk over time following vaccination with CoronaVac: test negative case-control study

OBJECTIVE

To estimate the change in odds of covid-19 over time following primary series completion of the inactivated whole virus vaccine CoronaVac (Sinovac Biotech) in São Paulo State, Brazil.

DESIGN

Test negative case-control study.

SETTING

Community testing for covid-19 in São Paulo State, Brazil.

PARTICIPANTS

Adults aged ≥18 years who were residents of São Paulo state, had received two doses of CoronaVac, did not have a laboratory confirmed SARS-CoV-2 infection before vaccination, and underwent reverse transcription polymerase chain reaction (RT-PCR) testing for SARS-CoV-2 from 17 January to 14 December 2021. Cases were matched to test negative controls by age (in 5 year bands), municipality of residence, healthcare worker status, and epidemiological week of RT-PCR test.

MAIN OUTCOME MEASURES

RT-PCR confirmed symptomatic covid-19 and associated hospital admissions and deaths. Conditional logistic regression was adjusted for sex, number of covid-19 associated comorbidities, race, and previous acute respiratory illness.

RESULTS

From 202 741 eligible people, 52 170 cases with symptomatic covid-19 and 69 115 test negative controls with covid-19 symptoms were formed into 43 257 matched sets. Adjusted odds ratios of symptomatic covid-19 increased with time since completion of the vaccination series. The increase in odds was greater in younger people and among healthcare workers, although sensitivity analyses suggested that this was in part due to bias. In addition, the adjusted odds ratios of covid-19 related hospital admission or death significantly increased with time compared with the odds 14-41 days after series completion: from 1.25 (95% confidence interval 1.04 to 1.51) at 70-97 days up to 1.94 (1.41 to 2.67) from 182 days onwards.

CONCLUSIONS

Significant increases in the risk of moderate and severe covid-19 outcomes occurred three months after primary vaccination with CoronaVac among people aged 65 and older. These findings provide supportive evidence for the implementation of vaccine boosters in these populations who received this inactivated vaccine. Studies of waning should include analyses designed to uncover common biases.

Real-world effectiveness of BNT162b2 vaccine against SARS-CoV-2 infection among adolescents (12 to 17-year-olds) in Malaysia

OBJECTIVES

In this study, we aimed to investigate vaccine effectiveness (VE) against SARS-CoV-2 infections among adolescents aged 12 to 17 years in Malaysia and examine potential VE differences after full vaccination.

METHODS

We consolidated data on COVID-19 testing, vaccination, and outcomes for all public school-going adolescents in Malaysia from September 1, 2021, to December 31, 2021, and estimated the VE against SARS-CoV-2 infections during this period. Cases were defined as positive tests, either by reverse transcriptase- PCR (RT-PCR) or rapid antigen (RTK-Ag) testing, while controls were negative tests. Secondarily, we restricted the analysis to all tests performed in December 2021 and compared VE by month of full vaccination.

RESULTS

A total of 175,880 eligible tests (53.4% or 93,995 RT-PCR tests) were included. After full vaccination with BNT162b2, VE against SARS-CoV-2 infections was 65.7% (95% confidence interval [CI] 64.4, 66.9) over the study period. When restricted to tests in December 2021, VEs for those fully vaccinated in September 2021, October 2021, and November 2021 were comparable (60.6% [95% CI 23.7, 81.5], 56.9% [95% CI 51.1, 62.0], and 65.7% [95% CI 59.8, 70.7] respectively).

CONCLUSIONS

Among adolescents, full vaccination with BNT162b2 offered considerable protection against SARS-CoV-2 infections over at least three months without substantial evidence of waning.