Background Vaccination is our main strategy to control SARS-CoV-2 infection. Given the decrease in quantitative SARS-CoV-2 spike 1–2 IgG antibody titers three months after the second BNT162b2 dose, healthcare workers received a third booster six months after completing the original protocol. This study aimed to analyze the quantitative SARS-CoV-2 spike 1–2 IgG antibody titers and the safety of the third dose. Material and methods A prospective longitudinal cohort study included healthcare workers who received a third booster six months after completing the BNT162b2 regimen. We assessed the quantitative SARS-CoV-2 spike 1–2 IgG antibody titers 21–28 days after the first and second dose, three months after the completed protocol, 1–7 days following the third dose, and 21–28 days after booster administration. Results The cohort comprised 168 participants aged 41(10) years old, 67% of whom were female. The third dose was associated with an increase in quantitative antibody titers, regardless of previous SARS-CoV-2 history. In cases with a negative SARS-CoV-2 history, the median (IQR) antibody titer values increased from 379 (645.4) to 2960 (2010) AU/ml, whereas in cases with a positive SARS-CoV-2 history, from 590 (1262) to 3090 (2080) AU/ml (p<0.001). The third dose caused a lower number of total (local and systemic) adverse events following immunization (AEFI) compared with the first two vaccines. However, in terms of specific symptoms such as fatigue, myalgia, arthralgia, fever, and adenopathy, the proportion was higher in comparison with the first and second doses (p<0.05). The most common AEFI after the third BNT162b2 vaccine was pain at the injection site (n = 82, 84.5%), followed by fatigue (n = 45, 46.4%) of mild severity (n = 36, 37.1%). Conclusion The third dose applied six months after the original BNT162b2 regimen increased the quantitative SARS-CoV-2 spike 1–2 IgG antibody titers. The booster dose was well tolerated and caused no severe AEFI.

BackgroundScarce information exists in relation to the comparison of seroconversion and adverse events following immunization (AEFI) with different SARS-CoV-2 vaccines. Our aim was to correlate the magnitude of the antibody response to vaccination with previous clinical conditions and AEFI.MethodsA multicentric comparative study where SARS-CoV-2 spike 1-2 IgG antibodies IgG titers were measured at baseline, 21-28 days after the first and second dose (when applicable) of the following vaccines: BNT162b2 mRNA, mRNA-1273, Gam-COVID-Vac, Coronavac, ChAdOx1-S, Ad5-nCoV and Ad26.COV2. Mixed model and Poisson generalized linear models were performed.ResultsWe recruited 1867 individuals [52 (SD 16.8) years old, 52% men]. All vaccines enhanced anti-S1 and anti-S2 IgG antibodies over time (p&lt;0.01). The highest increase after the first and second dose was observed in mRNA-1273 (p&lt;0.001). There was an effect of previous SARS-CoV-2 infection; and an interaction of age with previous SARS-CoV-2 infection, Gam-COVID-Vac and ChAdOx1-S (p&lt;0.01). There was a negative correlation of Severe or Systemic AEFI (AEs) of naïve SARS-CoV-2 subjects with age and sex (p&lt;0.001); a positive interaction between the delta of antibodies with Gam-COVID-Vac (p=0.002). Coronavac, Gam-COVID-Vac and ChAdOx1-S had less AEs compared to BNT162b (p&lt;0.01). mRNA-1273 had the highest number of AEFIs. The delta of the antibodies showed an association with AEFIs in previously infected individuals (p&lt;0.001).ConclusionsThe magnitude of seroconversion is predicted by age, vaccine type and SARS-CoV-2 exposure. AEs are correlated with age, sex, and vaccine type. The delta of the antibody response only correlates with AEs in patients previously exposed to SARS-CoV-2.Registration numberClinicalTrials.gov, identifier NCT05228912.

The efficacy of one dose Ad5-nCoV has been concerning. This study aimed to evaluate the effect of a single dose BNT162b2 in individuals after a completed Ad5-nCoV vaccination regiment compared to a group without this boost measuring SARS-CoV-2 Spike 1–2 IgG antibodies in plasma. This observational study included a subgroup analysis of patients who were immunized with Ad5-nCoV in a northern city of Mexico. During follow-up, some patients self-reported having received a BNT162b2 booster. We report baseline IgG levels, 21–28 days after the Ad5-nCoV dose, three months, and an additional 21–28 days after BNT162b2 (four months after Ad5-nCoV). Seventeen patients, age 40 (16), 52.9% men, were analyzed. We created four groups: G1 and G2 refer to patients without a history of SARS-CoV-2 infection, vaccinated with Ad5-nCoV and Ad5-nCoV/BNT162b2 (n = 4 and n = 6), respectively; G3 and G4 included patients with a history of SARS-CoV-2 infection and immunized with Ad5-nCoV and Ad5-nCoV/BNT162b2 (n = 5 and n = 2), respectively. The Ad5-nCoV/BNT162b2 protocol reported higher antibody titers after 21–28 days. Median (IQR) values were: G1 46.7 (-), G2 1077.5 (1901), G3 1158.5 (2673.5), and G4 2090 (-) (p < 0.05). Headache and pain at injection site were the most frequent adverse reactions associated with Ad5-nCoV (n = 10, 83%) and BNT162b2 (n = 5, 83.3%), respectively. Patients receiving BNT162b2 after Ad5-nCoV had higher SARS-CoV-2 spike 1–2 IgG antibody titers and had no severe adverse reactions.

Introduction: The efficacy with one dose Ad5-nCoV has been concerned. As a result, some patients have self-reported getting a boost with BNT. Therefore, this study aimed to compare SARS-CoV-2 spike 1-2 IgG antibodies in plasma samples between two groups: one group immunized with Ad5-nCoV and another with a heterologous vaccination regimen with Ad5-nCoV and BNT. Methods: Prospective observational study included a subgroup analysis of patients who received the Ad5-nCoV immunization during the first trimester of 2021 in a Northern city of Mexico; and agreed to a follow-up for an entire year through SARS-CoV-2 specific IgG antibodies measurement samples. During the three months follow-up, some patients self-reported receiving a BNT boost. We report IgG levels from basal, 21-28 days after Ad5-nCoV dose, three months, and an additional 21-28 days after BNT boost. Results: Seventeen patients 40 (16) years old, 52.9% men, were analyzed. We created four groups: (G1) patients vaccinated with Ad5-nCoV with no history of SARS-COV-2 (n=4), (G2) patients vaccinated with Ad5-nCoV and the first shot of BNT with no history of SARS-COV-2 (n=6), (G3) patients vaccinated with Ad5-nCoV with history of SARS-COV-2 (n=5), and (G4) patients vaccinated with Ad5-nCoV and the first shot of BNT with history of SARS-COV-2 (n=2). The group immunized with a heterologous vaccine scheme reported higher antibodies after 21-28 days of follow-up after BNT boost. Median (IQR): G1 46.7 (-), G2 1077.5 (1901), G3 1158.5 (2673.5), and G4 2090 (-) (p<0.05). Headache was the most frequent adverse reaction when patients received Ad5-nCoV (n = 10, 83%), and pain at the injection site was the most frequent adverse reaction with BNT boost (n = 5, 83.3%). Conclusion: Patients receiving a BNT boost after Ad5-nCoV had higher SARS-CoV-2 spike 1-2 IgG antibodies titers with no severe adverse reaction.