A Third Dose of an Inactivated Vaccine Dramatically Increased the Levels and Decay Times of Anti-SARS-CoV-2 Antibodies, but Disappointingly Declined Again: A Prospective, Longitudinal, Cohort Study at 18 Serial Time Points Over 368 Days

COVID-19 antibody responses in individuals with natural immunity and with vaccination-induced immunity: a systematic review and meta-analysis

BACKGROUND

The COVID-19 pandemic has caused a large mortality and morbidity burden globally. For individuals, a strong immune response is the most effective means to block SARS-CoV-2 infection. To inform clinical case management of COVID-19, development of improved vaccines, and public health policy, a better understanding of antibody response dynamics and duration following SARS-CoV-2 infection and after vaccination is imperatively needed.

METHODS

We systematically analyzed antibody response rates in naturally infected COVID-19 patients and vaccinated individuals. Specifically, we searched all published and pre-published literature between 1 December 2019 and 31 July 2023 using MeSH terms and "all field" terms comprising "COVID-19" or "SARS-CoV-2," and "antibody response" or "immunity response" or "humoral immune." We included experimental and observational studies that provided antibody positivity rates following natural COVID-19 infection or vaccination. A total of 44 studies reporting antibody positivity rate changes over time were included.

RESULTS

The meta-analysis showed that within the first week after COVID-19 symptom onset/diagnosis or vaccination, antibody response rates in vaccinated individuals were lower than those in infected patients (p < 0.01), but no significant difference was observed from the second week to the sixth month. IgG, IgA, and IgM positivity rates increased during the first 3 weeks; thereafter, IgG positivity rates were maintained at a relatively high level, while the IgM seroconversion rate dropped.

CONCLUSIONS

Antibody production following vaccination might not occur as quickly or strongly as after natural infection, and the IgM antibody response was less persistent than the IgG response.

SARS-CoV-2 booster vaccine dose significantly extends humoral immune response half-life beyond the primary series

SARS-CoV-2 lipid nanoparticle mRNA vaccines continue to be administered as the predominant prophylactic measure to reduce COVID-19 disease pathogenesis. Quantifying the kinetics of the secondary immune response from subsequent doses beyond the primary series and understanding how dose-dependent immune waning kinetics vary as a function of age, sex, and various comorbidities remains an important question. We study anti-spike IgG waning kinetics in 152 individuals who received an mRNA-based primary series (first two doses) and a subset of 137 individuals who then received an mRNA-based booster dose. We find the booster dose elicits a 71-84% increase in the median Anti-S half life over that of the primary series. We find the Anti-S half life for both primary series and booster doses decreases with age. However, we stress that although chronological age continues to be a good proxy for vaccine-induced humoral waning, immunosenescence is likely not the mechanism, rather, more likely the mechanism is related to the presence of noncommunicable diseases, which also accumulate with age, that affect immune regulation. We are able to independently reproduce recent observations that those with pre-existing asthma exhibit a stronger primary series humoral response to vaccination than compared to those that do not, and further, we find this result is sustained for the booster dose. Finally, via a single-variate Kruskal-Wallis test we find no difference between male and female humoral decay kinetics, however, a multivariate approach utilizing  Least Absolute Shrinkage and Selection Operator (LASSO) regression for feature selection reveals a statistically significant (p < 1 × 10 - 3 ), albeit small, bias in favour of longer-lasting humoral immunity amongst males.

Neutralizing antibody responses to SARS-CoV-2 Omicron variants: Post six months following two-dose & three-dose vaccination of ChAdOx1 nCoV-19 or BBV152

BACKGROUND OBJECTIVES

The Omicron sub-lineages are known to have higher infectivity, immune escape and lower virulence. During December 2022 - January 2023 and March - April 2023, India witnessed increased SARS-CoV-2 infections, mostly due to newer Omicron sub-lineages. With this unprecedented rise in cases, we assessed the neutralization potential of individuals vaccinated with ChAdOx1 nCoV (Covishield) and BBV152 (Covaxin) against emerging Omicron sub-lineages.

METHODS

Neutralizing antibody responses were measured in the sera collected from individuals six months post-two doses (n=88) of Covishield (n=44) or Covaxin (n=44) and post-three doses (n=102) of Covishield (n=46) or Covaxin (n=56) booster dose against prototype B.1 strain, lineages of Omicron; XBB.1, BQ.1, BA.5.2 and BF.7.

RESULTS

The sera of individuals collected six months after the two-dose and the three-dose demonstrated neutralizing activity against all variants. The neutralizing antibody (NAbs) level was highest against the prototype B.1 strain, followed by BA5.2 (5-6 fold lower), BF.7 (11-12 fold lower), BQ.1 (12 fold lower) and XBB.1 (18-22 fold lower).

INTERPRETATION CONCLUSIONS

Persistence of NAb responses was comparable in individuals with two- and three-dose groups post six months of vaccination. Among the Omicron sub-variants, XBB.1 showed marked neutralization escape, thus pointing towards an eventual immune escape, which may cause more infections. Further, the correlation of study data with complete clinical profile of the participants along with observations for cell-mediated immunity may provide a clear picture for the sustained protection due to three-dose vaccination as well as hybrid immunity against the newer variants.

Neutralizing Antibody Response following a Third Dose of the mRNA-1273 Vaccine among Cancer Patients

Cancer patients are at an increased risk of morbidity and mortality from SARS-CoV-2 infection and have a decreased immune response to vaccination. We conducted a study measuring both the neutralizing and total antibodies in cancer patients following a third dose of the mRNA-1273 COVID-19 vaccine. Immune responses were measured with an enzyme-linked immunosorbent assay (ELISA) and neutralization assays. Kruskal-Wallis tests were used to evaluate the association between patient characteristics and neutralization geometric mean titers (GMTs), and paired t-tests were used to compare the GMTs between different timepoints. Spearman correlation coefficients were calculated to determine the correlation between total antibody and neutralization GMTs. Among 238 adults diagnosed with cancer, a third dose of mRNA-1273 resulted in a 37-fold increase in neutralization GMT 28 days post-vaccination and maintained a 14.6-fold increase at 6 months. Patients with solid tumors or lymphoid cancer had the highest and lowest neutralization GMTs, respectively, at both 28 days and 6 months post-dose 3. While total antibody GMTs in lymphoid patients continued to increase, other cancer types showed decreases in titers between 28 days and 6 months post-dose 3. A strong correlation (p < 0.001) was found between total antibody and neutralization GMTs. The third dose of mRNA-1273 was able to elicit a robust neutralizing antibody response in cancer patients, which remained for 6 months after administration. Lymphoid cancer patients can benefit most from this third dose, as it was shown to continue to increase total antibody GMTs 6 months after vaccination.

RBD class 1 and 2 antibody epitopes elicit around 70% neutralizing capacity against SARS-CoV-2 virus following boosting with inactivated virus vaccine

A third dose of inactivated virus vaccine (IVV) boosts neutralizing antibodies, reducing SARS-CoV-2 transmission rate and COVID-19 severity. However, the impact of RBD-elicited antibodies and their neutralizing activity by the boost of IVV is unknown. We investigated the impact of IVV's boost shot on RBD-elicited antibodies and their neutralizing activity in 18 subjects receiving the second and third IVV doses. Using an RBD antibodies depletion assay, we assessed the neutralizing activity of RBD-elicited antibodies. After the second dose, RBD-antigen elicitation accounted for ∼60% of neutralizing activity, which increased to 82% after the IVV boost against ancestral SARS-CoV-2. Depleting class 3 and class 4-specific antibodies with the Beta-RBD protein revealed that NAbs targeting RBD class 1 and class 2 subdomains increased from 57% to 75% post-boost. These findings highlight the significant enhancement of RBD-specific antibodies, especially against RBD class 1 and class 2, with IVV booster doses. Our study offers valuable insights for optimizing COVID-19 vaccine strategies.

A community study of neutralizing antibodies against SARS-CoV-2 in China

Background

The immune background of the overall population before and after the outbreak of SARS-CoV-2 in China remains unexplored. And the level of neutralizing antibodies is a reliable indicator of individual immunity.

Objectives

This study aimed to assess the immune levels of different population groups during a viral outbreak and identify the factors influencing these levels.

Methods

We measured the levels of neutralizing antibodies in 12,137 participants using the COVID19 Neutralizing Antibody Detection kit. The dynamics of neutralizing antibodies were analyzed using a generalized additive model, while a generalized linear model and multi-factor analysis of variance were employed to investigate the influencing factors. Additionally, statistical methods were used to compare neutralizing antibody levels among subgroups of the real-world population.

Results

Participants who received booster doses exhibited significantly higher levels of neutralizing antibodies compared to those who received only one or two doses (p<0.001). Both elderly [22.55 (5.12, 62.03) IU/mL, 55%] and minors [21.41 (8.15, 45.06) IU/mL, 56%] showed lower positivity rates and neutralizing antibody levels compared to young adults [29.30 (9.82, 188.08) IU/mL, 62%] (p<0.001). Furthermore, the HIV-positive group demonstrated a slightly lower seropositivity rate compared to the healthy group across the three vaccination time points. Notably, three months after the large-scale infection, both the neutralizing antibody level and positivity rate in real-world populations were higher than the previous record [300 (300, 300) IU/mL, 89%; 27.10 (8.77, 139.28) IU/mL, 60%], and this difference was statistically significant.

Conclusions

Increasing vaccine dosage enhances neutralizing antibody levels, resulting in greater and longer-lasting immunity. Monitoring immune levels in older individuals and those with AIDS is crucial. Additionally, the neutralizing antibodies generated from vaccination have not yet reached the threshold for achieving herd immunity, while individuals exhibit higher immune levels following a large-scale infection. These findings provide valuable insights for guiding new strategies in vaccine administration.

Are people living with HIV have a low vulnerability to omicron variant infection: results from a cross-sectional study in China

BACKGROUND

A surge of more than 80 million Omicron variant infected cases was reported in China less than a month after the "zero COVID" strategy ended on December 7, 2022. In this circumstance, whether people living with HIV (PLWH) in China experience a similar risk is not clear.

METHODS

A cross-sectional study was conducted in the Wuchang District of Wuhan between December 20, 2022, and January 18, 2023 through a self-administered online survey. PLWH and HIV-negative people aged ≥ 18 years old who volunteered for this survey were eligible. The prevalence of Omicron variant infection between PLWH and HIV-negative people was compared, and the factors associated with the Omicron variant infection among PLWH and HIV-negative people were further evaluated, respectively.

RESULTS

In total, 890 PLWH and 1,364 HIV-negative adults from Wuchang District were enrolled. Among these participants, 690 PLWH (77.5%) and 1163 HIV-negative people (85.3%) reported SARS-CoV-2 infection. Gender, chronic disease conditions, and COVID-19 vaccination status significantly differed between the two groups. After adjusting gender, age, comorbidities, and COVID-19 vaccination status, the risk of SARS-CoV-2 infection among PLWH was significantly lower than among HIV-negative people (aOR 0.56, 95%CI 0.42-0.76). Multivariable logistic regression analysis showed that PLWH with older age and detectable HIV-viral load (HIV-VL) had decreased risk of SARS-CoV-2 infection (aOR 0.98, 95%CI 0.96-0.99; aOR 0.59, 95%CI 0.36-0.97). Compared with PLWH receiving one/two doses of COVID-19 vaccines, no significant differences in the risk of SARS-CoV-2 infection were observed among PLWH receiving three doses of inactivated vaccines and four doses of vaccines (three doses of inactivated vaccines plus one dose of inhaled recombinant adenovirus type 5 (AD5)-vectored vaccine). Among HIV-negative people, those receiving four doses of COVID-19 vaccines had a lower risk of SARS-CoV-2 infection than those receiving one/two doses (aOR 0.14, 95%CI 0.08-0.25).

CONCLUSIONS

Our study proves that PLWH have a lower risk of Omicron variant infection than HIV-negative people. However, even PLWH with younger age and virological suppression should strengthen the prevention against SARS-CoV-2 infection. Three doses of inactivated vaccines plus one dose of inhaled recombinant AD5-vectored COVID-19 vaccine may provide better protection for HIV-negative people.

Vaccination Status and In-hospital Mortality Among Adults With COVID-19 in Jakarta, Indonesia: A Retrospective Hospital-based Cohort Study

OBJECTIVES

Prospective studies on vaccination status and mortality related to coronavirus disease 2019 (COVID-19) in low-resource settings are still limited. We assessed the association between vaccination status (full, partial, or none) and in-hospital mortality among COVID-19 patients at most hospitals in Jakarta, Indonesia during the Delta predomination wave.

METHODS

We conducted a retrospective cohort study among hospitalized COVID-19 patients who met the study criteria (>18 years old and admitted for inpatient treatment because of laboratory-confirmed severe acute respiratory syndrome coronavirus 2 infection). We linked individual-level data in the hospital admission database with vaccination records. Several socio-demographic and clinical characteristics were also analyzed. A Cox proportional hazards regression model was used to explore the association between vaccination status and in-hospital mortality in this patient group.

RESULTS

In total, 40 827 patients were included in this study. Of these, 70% were unvaccinated (n=28 543) and 19.3% (n=7882) died during hospitalization. The mean age of the patients was 49 years (range, 35-59), 53.2% were female, 22.0% had hypertension, and 14.2% were treated in the intensive care unit, and the median hospital length of stay across the group was 9 days. Our study showed that the risk of in-hospital mortality among fully and partially vaccinated patients was lower than among unvaccinated adults (adjusted hazard ratio [aHR], 0.43; 95% confidence interval [CI], 0.40 to 0.47 and aHR, 0.70; 95% CI, 0.64 to 0.77, respectively).

CONCLUSIONS

Vaccinated patients had fewer severe outcomes among hospitalized adults during the Delta wave in Jakarta. These features should be carefully considered by healthcare professionals in treating adults within this patient group.

Trends of participants in convalescent plasma donation for COVID-19 in Japan as the pandemic evolved

Background

We aimed to investigate chronological changes in the characteristics of participants in a coronavirus disease 2019 convalescent plasma donation study that may benefit optimal collection methods in the future.

Methods

Data from a convalescent plasma donation study from April 30, 2020 to November 5, 2021 were collected and analyzed. After August 23, 2021, an interim analysis of factors linked to higher antibody titers led us to restrict our participant recruitment criteria to participants who were within 4 months of disease onset and to patients who were otherwise most likely to have sufficiently high antibody titers. Overall, 1299 samples from 1179 patients were analyzed.

Results

Over the duration of the study, 35.9% of the samples were deemed eligible for convalescent plasma collection. The overall eligibility rate initially declined, dipping to <20% after one year. During this period, the proportion of enrolled samples from patients who had severe illness also declined, and the proportion of samples from participants who were >120 days post disease onset increased. After the addition of days from onset and vaccination status to our participant recruitment criteria, the eligibility rate improved significantly.

Conclusions

As outbreaks of emerging infectious disease occur, it is desirable to construct and implement a scheme for convalescent plasma donation promptly and to monitor the eligibility rate over time. If it declines, promptly analyze and resolve the associated factors. Additionally, vaccine development and infection prevalence are likely to influence the effective recruitment of participants with high antibody titers.

Heterologous DNA-prime/protein-boost immunization with a monomeric SARS-CoV-2 spike antigen redundantizes the trimeric receptor-binding domain structure to induce neutralizing antibodies in old mice

A multitude of alterations in the old immune system impair its functional integrity. Closely related, older individuals show, for example, a reduced responsiveness to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccines. However, systematic strategies to specifically improve the efficacy of vaccines in the old are missing or limited to simple approaches like increasing the antigen concentration or injection frequencies. We here asked whether the intrinsic, trimeric structure of the SARS-CoV-2 spike (S) antigen and/or a DNA- or protein-based antigen delivery platform affects priming of functional antibody responses particularly in old mice. The used S-antigens were primarily defined by the presence/absence of the membrane-anchoring TM domain and the closely interlinked formation/non-formation of a trimeric structure of the receptor binding domain (S-RBD). Among others, we generated vectors expressing prefusion-stabilized, cell-associated (TM+) trimeric "S2-P" or secreted (TM-) monomeric "S6-PΔTM" antigens. These proteins were produced from vector-transfected HEK-293T cells under mild conditions by Strep-tag purification, revealing that cell-associated but not secreted S proteins tightly bound Hsp73 and Grp78 chaperones. We showed that both, TM-deficient S6-PΔTM and full-length S2-P antigens elicited very similar S-RBD-specific antibody titers and pseudovirus neutralization activities in young (2-3 months) mice through homologous DNA-prime/DNA-boost or protein-prime/protein-boost vaccination. The trimeric S2-P antigen induced high S-RBD-specific antibody responses in old (23-24 months) mice through DNA-prime/DNA-boost vaccination. Unexpectedly, the monomeric S6-PΔTM antigen induced very low S-RBD-specific antibody titers in old mice through homologous DNA-prime/DNA-boost or protein-prime/protein-boost vaccination. However, old mice efficiently elicited an S-RBD-specific antibody response after heterologous DNA-prime/protein-boost immunization with the S6-PΔTM antigen, and antibody titers even reached similar levels and neutralizing activities as in young mice and also cross-reacted with different S-variants of concern. The old immune system thus distinguished between trimeric and monomeric S protein conformations: it remained antigen responsive to the trimeric S2-P antigen, and a simple change in the vaccine delivery regimen was sufficient to unleash its reactivity to the monomeric S6-PΔTM antigen. This clearly shows that both the antigen structure and the delivery platform are crucial to efficiently prime humoral immune responses in old mice and might be relevant for designing "age-adapted" vaccine strategies.

Safety and immunogenicity of Ad5-nCoV immunization after three-dose priming with inactivated SARS-CoV-2 vaccine in Chinese adults

Data on the safety and immunity of a heterologous booster (fourth dose) after three-doses of inactivated SARS-CoV-2 vaccine in Chinese adults are limited. We evaluate the safety and immunogenicity of Ad5-nCoV in a randomized, double-blind, parallel-controlled phase 4 clinical trial in Zhejiang, China (NCT05373030). Participants aged 18-80 years (100 per group), administered three doses of inactivated SARS-CoV-2 vaccine ≥6 months earlier, are enrolled and randomized 1:1 into two groups, which are administered intramuscular Ad5-nCoV or inactivated SARS-CoV-2 vaccine (CoronaVac or Covilo). All observed adverse reactions are predictable and manageable. Ad5-nCoV elicits significantly higher RBD-specific IgG levels, with a geometric mean concentration of 2924.0 on day 14 post-booster, 7.8-fold that of the inactivated vaccine. Pseudovirus-neutralizing antibodies to Omicron BA.4/5 show a similar pattern, with geometric mean titers of 228.9 in Ad5-nCoV group and 65.5 in inactivated vaccine group. Ad5-nCoV booster maintains high antibody levels on day 90, with seroconversion of 71.4%, while that of inactivated vaccine is 5.2%, almost pre-booster levels. A fourth Ad5-nCoV vaccination following three-doses of inactivated SARS-CoV-2 vaccine is immunogenic, tolerable, and more efficient than inactivated SARS-CoV-2 vaccine. Ad5-nCoV elicits a stronger humoral response against Omicron BA.4/5 and maintains antibody levels for longer than homologous boosting.

A tale of two conditions: when people living with HIV meet three doses of inactivated COVID-19 vaccines

Background

Currently, data on long-term immune responses to a homogenous booster dose of the inactivated COVID-19 vaccine are still limited among people living with HIV (PLWH).

Methods

A prospective cohort study with a 13-month follow-up was conducted in China between March 2021 and August 2022 to evaluate the dynamics of SARS-CoV-2 specific humoral and cellular immunity against three doses of the inactivated COVID-19 vaccine from before the first dose until 6 months after the booster dose vaccination among PLWH in comparison to healthy controls (HC).

Results

43 PLWH on antiretroviral therapy (ART) and 23 HC were enrolled. Compared with HC, the neutralizing antibodies (nAbs) levels among PLWH were significantly lower on days 14, 30, 60, 90, and 120 after the booster dose vaccination. Among PLWH, the nAbs titers on days 14, 30, and 60 after the booster dose were significantly higher than the peak of the second dose. However, on day 180 after the booster dose, the nAbs titers were similar to the peak of the second dose vaccination. Compared with HC, the frequencies of IFN-γ-secreting and TNF-α-secreting CD4⁺ and CD8⁺ T cells among PLWH were lower on days 14 and 180 after the booster dose vaccination. Among PLWH, increased T cell immunity was induced by the booster dose of the vaccine and kept stable on day 180 after the booster dose vaccination.

Conclusion

Although a homogenous booster dose following two doses of the inactivated COVID-19 vaccine among PLWH could elicit higher nAb titers, reduce antibody decay, and maintain T cell responses even 6 months after vaccination, the overall immunogenicity of the booster dose was found to be lower among PLWH than among healthy controls. Further strategies are needed to improve immunogenicity to the inactivated COVID-19 vaccine among PLWH.

Durability of immune response after SARS-CoV-2 vaccination in patients with chronic liver disease

Aim

The present study aimed to evaluate the durability of immune response after basic and booster immunization with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines in patients with chronic liver disease (CLD).

Methods

Patients with CLD and complete basic or booster immunization with SARS-CoV-2 vaccines were included in this study. Based on the vaccination situation, they were divided into the basic immunity group (Basic) and the booster immunity group (Booster), which were then subdivided into four groups according to the time interval from completion of basic immunization or booster immunization to serological specimen collection. The positive rates and antibody titers of novel coronavirus neutralizing antibody (nCoV NTAb) and novel coronavirus spike receptor-binding domain antibody (nCoV S-RBD) were analyzed.

Results

A total of 313 patients with CLD were enrolled in this study, including 201 in Basic and 112 in Booster. The positive rates of nCoV NTAb and nCoV S-RBD within 30 days of completing basic immunization were 80.4% and 84.8%, respectively, but decreased rapidly with the extension of vaccination time, and only 29% and 48.4% of patients with CLD remained positive for nCoV NTAb and nCoV S-RBD, respectively, after 120 days of completing basic immunization. Within 30 days of booster immunization, the positive rates of nCoV NTAb and nCoV S-RBD in patients with CLD rapidly increased from 29.0% and 48.4% at the end of basic immunization to 95.2% and 90.5%, and maintained a high level (defined as the positive rate >50%) until 120 days when the positive rates of nCoV NTAb and nCoV S-RBD were still high at 79.5% and 87.2%, respectively. After basic immunization, the time for nCoV NTAb and nCoV S-RBD to turn negative was 120 and 169 days, respectively, and the negative time of nCoV NTAb and nCoV S-RBD was significantly prolonged to 266 days and 329 days, respectively.

Conclusion

It is safe and effective for patients with CLD to complete basic and booster immunization with SARS-CoV-2 vaccines. After booster immunization, the immune response of patients with CLD was further improved and the durability of the SARS-CoV-2 antibody was significantly prolonged.

Dynamic immunogenicity after primary and booster inactivated SARS-CoV-2 vaccination in people living with HIV: A longitudinal observational study

People living with HIV (PLWH) have poor outcomes from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); vaccination reduces the associated mortality. The humoral immune response dynamics after booster inactivated vaccinations in PLWH remain unclear. In this longitudinal observational study, 100 PLWH after primary inactivated SARS-CoV-2 vaccination were consecutively recruited and followed up. After booster vaccination (BV), neutralizing antibodies (NAbs) were detected at 1 month from all the PLWH, and the titer increased sixfold compared to that associated with the primary vaccination (PV), similar to that in healthy controls after BV. The NAbs titer declined over time after BV, but remained higher at 6 months than after PV. The NAbs response was elevated after BV with CD4 count <200 cells/μL, it was the poorest among the different CD4 cell count subgroups. Similar results were observed for anti-RBD-IgG responses. Moreover, RBD-specific MBCs were significantly elevated after BV in PLWH. No serious AEs were observed after BV in PLWH. In conclusion, booster inactivated SARS-CoV-2 vaccination is well tolerated and can elicit robust and durable humoral responses in PLWH. PLWH may benefit from a third dose of the inactivated vaccine.

Successful clearance of persistent SARS-CoV-2 asymptomatic infection following a single dose of Ad5-nCoV vaccine

Persistent asymptomatic (PA) SARS-CoV-2 infections have been identified. The immune responses in these patients are unclear, and the development of effective treatments for these patients is needed. Here, we report a cohort of 23 PA cases carrying viral RNA for up to 191 days. PA cases displayed low levels of inflammatory and interferon response, weak antibody response, diminished circulating follicular helper T cells (cTfh), and inadequate specific CD4⁺ and CD8⁺ T-cell responses during infection, which is distinct from symptomatic infections and resembling impaired immune activation. Administration of a single dose of Ad5-nCoV vaccine to 10 of these PA cases elicited rapid and robust antibody responses as well as coordinated B-cell and cTfh responses, resulting in successful viral clearance. Vaccine-induced antibodies were able to neutralize various variants of concern and persisted for over 6 months, indicating long-term protection. Therefore, our study provides an insight into the immune status of PA infections and highlights vaccination as a potential treatment for prolonged SARS-CoV-2 infections.

Subjects who developed SARS-CoV-2 specific IgM after vaccination show a longer humoral immunity and a lower frequency of infection

BACKGROUND

We have previously shown that eliciting SARS-CoV-2-specific IgM after vaccination is associated with higher levels of SARS-CoV-2 neutralizing IgG. This study aims to assess whether IgM development is also associated with longer-lasting immunity.

METHODS

We analysed anti-SARS-CoV-2 spike protein IgG and IgM (IgG-S, IgM-S), and anti-nucleocapsid IgG (IgG-N) in 1872 vaccinees at different time points: before the first dose (D1; w0), before the second dose (D2; w3) at three (w6) and 23 weeks (w29) after D2; moreover, 109 subjects were further tested at the booster dose (D3, w44), at 3 weeks (w47) and 6 months (w70) after D3. Two-level linear regression models were used to evaluate the differences in IgG-S levels.

FINDINGS

In subjects who had no evidence of a previous infection at D1 (non-infected, NI), IgM-S development after D1 and D2 was associated with higher IgG-S levels at short (w6, p < 0.0001) and long (w29, p < 0.001) follow-up. Similar IgG-S levels were observed after D3. The majority (28/33, 85%) of the NI subjects who had developed IgM-S in response to vaccination did not experience infection.

INTERPRETATION

The development of anti-SARS-CoV-2 IgM-S following D1 and D2 is associated with higher IgG-S levels. Most individuals who developed IgM-S never became infected, suggesting that IgM elicitation may be associated with a lower risk of infection.

FUNDING

"Fondi Ricerca Corrente" and "Progetto Ricerca Finalizzata" COVID-2020 (Italian Ministry of Health); FUR 2020 Department of Excellence 2018-2022 (MIUR, Italy); the Brain Research Foundation Verona.

Homologous booster immunization with an inactivated vaccine induced robust antibody response in healthcare workers: A retrospective study

Coronavirus Disease 2019 (Covid-19) severely impacted the health, society, and economy around the world. With declining protective efficacy of primary vaccination and the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants, a Covid-19 booster vaccination is being fully implemented globally. Many people received three doses of BBIBP-CorV inactivated vaccine in China and other developing countries. However, the antibody response and immune persistence of the homologous BBIBP-CorV booster vaccination is yet to be thoroughly evaluated, as previous studies focused within one month after the third dose. In this study, 97 participants were enrolled to analyze the antibody response and immune persistence within 6 months as well as the safety within 7 days after the third-dose of homologous BBIBP-CorV inactivated vaccine. The seroconversion rate for total antibody against the receptor binding domain (RBD) of the SARS-CoV-2 spike (S) protein were both 100% at month 1 and month 6 after the third dose. The IgG against the RBD of the SARS-CoV-2 S protein seroconversion rate increased from 42.27% before the third dose to 100% 1 month after the third dose and then slightly decreased to 98.97% 5 months later. Positive IgM against the RBD of the SARS-CoV-2 S protein was rare and was observed in only one participant at month 1 after the third dose. The neutralizing antibody levels at month 1 and month 6 after the third dose increased 63.32-fold and 13.16-fold compared with those before the third dose, and the positive rate for neutralizing antibody was still 100% at month 6 after the third dose. Importantly, the antibody responses induced by the vaccine and immune persistence were not affected by sex or age. No serious adverse reactions were reported. Total antibody and IgG against the RBD of the SARS-CoV-2 S protein were highly correlated with neutralizing antibody, suggesting that total antibody and IgG against the RBD of the SARS-CoV-2 S protein could be used as predictors for neutralizing antibody. In conclusion, the third dose of homologous BBIBP-CorV inactivated vaccine induced a robust antibody response and moderate immune persistence. These finding are of great significance for development future vaccination strategies.

Anti-SARS-CoV-2 IgM Secondary Response Was Suppressed by Preexisting Immunity in Vaccinees: A Prospective, Longitudinal Cohort Study over 456 Days

To obtain more insight into IgM in anti-SARS-CoV-2 immunity a prospective cohort study was carried out in 32 volunteers to longitudinally profile the kinetics of the anti-SARS-CoV-2 IgM response induced by administration of a three-dose inactivated SARS-CoV-2 vaccine regimen at 19 serial time points over 456 days. The first and second doses were considered primary immunization, while the third dose was considered secondary immunization. IgM antibodies showed a low secondary response that was different from the other three antibodies (neutralizing, total, and IgG antibodies). There were 31.25% (10/32) (95% CI, 14.30-48.20%) of participants who never achieved a positive IgM antibody conversion over 456 days after vaccination. The seropositivity rate of IgM antibodies was 68.75% (22/32) (95% CI, 51.80-85.70%) after primary immunization. Unexpectedly, after secondary immunization the seropositivity response rate was only 9.38% (3/32) (95% CI, 1.30-20.10%), which was much lower than that after primary immunization (p = 0.000). Spearman's correlation analysis indicated a poor correlation of IgM antibodies with the other three antibodies. IgM response in vaccinees was completely different from the response patterns of neutralizing, total, and IgG antibodies following both the primary immunization and the secondary immunization and was suppressed by pre-existing immunity induced by primary immunization.

Short-Term Adverse Effects Following Booster Dose of Inactivated-Virus vs. Adenoviral-Vector COVID-19 Vaccines in Algeria: A Cross-Sectional Study of the General Population

COVID-19 booster vaccines have been adopted in almost all countries to enhance the immune response and combat the emergence of new variants. Algeria adopted this strategy in November 2021. This study was conducted to consider the self-reported side effects of COVID-19 booster vaccines by Algerians who were vaccinated with a booster dose of one of the approved inactivated-virus vaccines, such as BBIBP-CorV and CoronaVac, or one of the adenoviral-vector-based vaccines, such as Gam-COVID-Vac, AZD1222 and Ad26.COV2.S, and to determine the eventual risk factors. A cross-sectional study using an online self-administered questionnaire (SAQ) was conducted in Algeria between 28 April 2022, and 20 July 2022. A descriptive analysis of the 196 individuals who were included showed a nearly equal distribution of adenoviral- (52%) and inactivated-virus vaccines (48%) and of males (49.5%) and females (50.5%). The results showed that 74.7% of the studied population reported at least one local or systemic side effect. These side effects were more frequent among adenoviral-vector vaccinees (87.3%) than inactivated-virus vaccinees (60.6%) (sig. < 0.001). Injection site pain (40.3%), heat at the injection site (21.4%), and arm pain (16.3%) were the most common local side effects. These signs generally appeared in the first 12 h (73.3%) and generally lasted less than 24 h (32.8%). More interestingly, these signs differed from those that followed the administration of primer doses (48.5%) and were generally more severe (37%). The same observation was reported for systemic side effects, where the signs were especially most severe in the adenoviral-vaccinated group (49.4% vs. 20.8%; sig. = 0.001). These signs generally appeared within the first day (63.6%) and mostly disappeared before two days (50.8%), with fatigue (41.8%), fever (41.3%), and headache (30.1%) being the most common. Adenoviral-vector vaccinees (62.7%) were more likely to use medications to manage these side effects than were inactivated-virus vaccinees (45.7%) (sig. = 0.035) and paracetamol (48.5%) was the most used medication. Adenoviral-based vaccines were the types of vaccines that were most likely to cause side effects. In addition, being female increased the risk of developing side effects; regular medication was associated with local side effects among inactivated-virus vaccinees; and previous infection with COVID-19 was associated with systemic and local side effects among adenovirus-based vaccinees. These results support the short-term safety of booster vaccines, as has been reported for primer doses.

Comparison of SARS-CoV-2 Antibody Levels after a Third Heterologous and Homologous BNT162b2 Booster Dose

This study aimed to determine the anti-S (receptor binding protein) RBD IgG antibody titers formed against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV2) and the neutralizing antibody inhibition percentages (nAb IH%) in blood samples taken after two doses of inactive or mRNA-based vaccine and a booster dose. Volunteers with two doses of inactivated CoronaVac (heterologous group; n = 75) and BioNTech (BNT)162b2 mRNA vaccine (homologous group; n = 75) were included in this study. All participants preferred the BNT162b2 vaccine as a booster dose. First, peripheral blood samples were taken 3 months after the second vaccine dose. Second, peripheral blood samples were taken 1 month after the booster dose. Anti-S-RBD IgG titers were determined by CMIA (SARS-CoV-2 IgG II Quant). Neutralizing antibodies were detected by a surrogate neutralization assay (SARS-CoV-2 NeutraLISA, Euroimmun, Lübeck, Germany). The median age of the volunteers was 40 (IQR 29-47) years old. After the heterologous booster dose, anti-S-RBD IgG levels and neutralizing antibodies increased approximately 50-fold and 9-fold, respectively. Anti-S-RBD IgG titers increased by 9 and 57 times, respectively, while nAb IH% increased by 1.5 and 16 times, respectively, among those with heterologous reminder doses and those with and without a prior history of coronavirus disease (COVID-19). This study showed that after the administration of a heterologous booster dose with BNT162b2 to those whose primary vaccination was with inactivated CoronaVac, the binding and neutralizing antibody levels were similar to those who received a homologous BNT162b2 booster dose. It was observed that the administration of heterologous and homologous booster doses resulted in the development of similar levels of neutralizing antibodies, independently from a prior history of COVID-19.

Three-Dose Primary Series of Inactivated COVID-19 Vaccine for Persons Living with HIV, Hong Kong

In a cohort of persons living with HIV in Hong Kong, surrogate virus neutralization testing for COVID-19 yielded a median level of 89% after the third dose of an inactivated COVID-19 vaccine, compared with 37% after the second dose. These results support using a 3-dose primary series for enhanced immune protection.

Distinct immune responses in the early phase to natural SARS-CoV-2 infection or vaccination

Immune responses elicited by viral infection or vaccination play key roles in the viral elimination and the prevention of reinfection, as well as the protection of healthy persons. As one of the most widely used Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines, there have been increasing concerns about the necessity of additional doses of inactivated vaccines, due to the waning immune response several months after vaccination. To further optimize inactivated SARS-CoV-2 vaccines, we compared immune responses to SARS-CoV-2 elicited by natural infection and immunization with inactivated vaccines in the early phase. We observed the lower antibody levels against SARS-CoV-2 spike (S) and nucleocapsid (N) proteins in the early phase of postvaccination with a slow increase, compared to the acute phase of SARS-CoV-2 natural infection. Specifically, IgA antibodies have the most significant differences. Moreover, we further analyzed cytokine expression between these two groups. A wide variety of cytokines presented high expression in the infected individuals, while a few cytokines were elicited by inactivated vaccines. The differences in antibody responses and cytokine levels between natural SARS-CoV-2 infection and vaccination with the inactivated vaccines may provide implications for the optimization of inactivated SARS-CoV-2 vaccines and the additional application of serological tests.

Technical performance of a lateral flow immunoassay for detection of anti-SARS-CoV-2 IgG in the outpatient follow-up of non-severe cases and at different times after vaccination: comparison with enzyme and chemiluminescent immunoassays

This study assessed the technical performance of a rapid lateral flow immunochromatographic assay (LFIA) for the detection of anti-SARS-CoV-2 IgG and compared LFIA results with chemiluminescent immunoassay (CLIA) results and an in-house enzyme immunoassay (EIA). To this end, a total of 216 whole blood or serum samples from three groups were analyzed: the first group was composed of 68 true negative cases corresponding to blood bank donors, healthy young volunteers, and eight pediatric patients diagnosed with other coronavirus infections. The serum samples from these participants were obtained and stored in a pre-COVID-19 period, thus they were not expected to have COVID-19. In the second group of true positive cases, we chose to replace natural cases of COVID-19 by 96 participants who were expected to have produced anti-SARS-CoV-2 IgG antibodies 30-60 days after the vaccine booster dose. The serum samples were collected on the same day that LFIA were tested either by EIA or CLIA. The third study group was composed of 52 participants (12 adults and 40 children) who did or did not have anti-SARS-CoV-2 IgG antibodies due to specific clinical scenarios. The 12 adults had been vaccinated more than seven months before LFIA testing, and the 40 children had non-severe COVID-19 diagnosed using RT-PCR during the acute phase of infection. They were referred for outpatient follow-up and during this period the serum samples were collected and tested by CLIA and LFIA. All tests were performed by the same healthcare operator and there was no variation of LFIA results when tests were performed on finger prick whole blood or serum samples, so that results were grouped for analysis. LFIA's sensitivity in detecting anti-SARS-CoV-2 IgG antibodies was 90%, specificity 97.6%, efficiency 93%, PPV 98.3%, NPV 86.6%, and likelihood ratio for a positive or a negative result were 37.5 and 0.01 respectively. There was a good agreement (Kappa index of 0.677) between LFIA results and serological (EIA or CLIA) results. In conclusion, LFIA analyzed in this study showed a good technical performance and agreement with reference serological assays (EIA or CLIA), therefore it can be recommended for use in the outpatient follow-up of non-severe cases of COVID-19 and to assess anti-SARS-CoV-2 IgG antibody production induced by vaccination and the antibodies decrease over time. However, LFIAs should be confirmed by using reference serological assays whenever possible.