RESUMO
The high number of mutations in the Omicron variant of SARS-CoV-2 cause its immune escape when compared to the earlier variants of concern (VOC). At least three vaccine doses are required for the induction of Omicron neutralizing antibodies and further reducing the risk for hospitalization. However, most of the studies have focused on the immediate response after the booster vaccination while the duration of immune response is less known. We here studied longitudinal serum samples from the vaccinated individuals up to three months after their third dose of the BNT162b2 vaccine for their capacity to produce protective antibodies and T cell responses to Wuhan and Omicron variants. After the second dose, the antibody levels to the unmutated spike protein were significantly decreased at three months, and only 4% of the individuals were able to inhibit Omicron spike interaction compared to 47%, 38%, and 14% of individuals inhibiting wild-type, delta, and beta variants spike protein. Nine months after the second vaccination, the antibody levels were similar to the levels before the first dose and none of the sera inhibited SARS-CoV-2 wild-type or any of the three VOCs. The booster dose remarkably increased antibody levels and their ability to inhibit all variants. Three months after the booster the antibody levels and the inhibition activity were trending lower but still up and not significantly different from their peak values at two weeks after the third dose. Although responsiveness towards mutated spike peptides was lost in less than 20 % of vaccinated individuals, the wild-type spike-specific CD4+ and CD8+ memory T cells were still present at three months after the booster vaccination in the majority of studied individuals. Our data show that two doses of the BNT62b2 vaccine are not sufficient to protect against the Omicron variant, however, the spike-specific antibodies and T cell responses are strongly elicited and well maintained three months after the third vaccination dose.
RESUMO
BackgroundThe mRNA vaccines for SARS-CoV2 have proven highly effective and are currently used to vaccinate all age groups against COVID-19. Despite their high efficacy in clinical trials, there is limited data on the impact of age, sex, and side effects on vaccine-induced immune responses. MethodsWe here studied the development of SARS-CoV-2 Spike protein RBD domain antibodies after two doses of the Pfizer-BioNTech Comirnaty mRNA vaccine in 118 healthy volunteers and correlated their immune response with age, sex, and side effects reported after the vaccinations. FindingsOur findings show a robust immune response to the Spike proteins RBD region after the first and the second vaccination dose. However, we also saw a decline of antibody levels at 6 weeks versus 1 week after the second dose, suggesting a waning of the immune response over time. Regardless of this, the antibody levels at 6 weeks after the second dose remained significantly higher than before the vaccination, after the first dose, or in COVID-19 convalescent individuals. We found a decreased vaccination efficacy but fewer adverse events in older individuals, and that mRNA vaccination is less efficient in older males whereas the detrimental impact of age on vaccination outcome is abolished in females at 6 weeks after the second dose. InterpretationThe Pfizer-BioNTech Comirnaty mRNA vaccine induces a strong immune response after two doses of vaccination but older individuals develop fewer side effects and decreased antibody levels at 6 weeks. The waning of anti-viral antibodies in particular in older male individuals suggests that both age and male sex act as risk factors in the immune response to the SARS-CoV-2 mRNA vaccine. FundingThe study was supported by the Centre of Excellence in Translational Genomics (EXCEGEN), and the Estonian Research Council grant PRG377 and SYNLAB Estonia. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSThe first studies addressing the immune responses in older individuals after the single-dose administration of the SARS-CoV-2 mRNA vaccines have been published. We searched PubMed and medRxiv for publications on the immune response of SARS-CoV-2-mRNA vaccines, published in English, using the search terms "SARS-CoV-2", "COVID-19", "vaccine response", "mRNA vaccine", up to April 15th, 2021. To date, most mRNA vaccine response studies have not been peer-reviewed, and data on the role of age, sex and side effects on SARS-CoV-2-mRNA vaccines in real vaccination situations is limited. Some studies have found a weaker immune response in older individuals after the first dose and these have been measured at a relatively short period (within 1-2 weeks) after the first dose but little longer-term evidence exists on the postvaccination antibody persistence. Even less information is available on sex differences or correlations with mRNA vaccine side effects. Added value of this studyIn this study, we assessed the antibody response up to 6 weeks after the second dose of Pfizer-BioNTech Comirnaty mRNA vaccine in 118 individuals. Our findings show a strong initial immune response after the first dose and an even higher Spike RBD antibody levels at 1 week after the second dose, but these significantly declined at 6 weeks after the second dose. We also found a weaker immune response and faster waning of antibodies in older vaccinated individuals, which correlated with fewer side effects at the time of vaccinations. Furthermore, although overall female and male vaccinees responded similarly, we found that age-related waning of the vaccine-related antibodies was stronger amongst older males whereas in females the impact of age was lost at 6 weeks after the second dose. Implications of all the available evidenceNew mRNA vaccines are now applied worldwide as they have shown high efficacy in clinical trials. Our results show that two doses of Pfizer-BioNTech Comirnaty mRNA vaccine induce a strong antibody response to Spike RBD region but these high levels decline 1.5 months after the second dose in most of the vaccinated individuals. Nevertheless, even at 6 weeks after the second dose, they stay significantly higher than at prevaccination, after the first dose of vaccine, or in Covid-19 postinfection. These findings also implicate that fewer adverse effects may indicate lower antibody response after the vaccination and point to the need for more individualized vaccination protocols, in particular among older people.
