Protective antibodies and T cell responses to Omicron variant three months after the booster dose of BNT162b2 vaccine (preprint)

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.

Declined Antibody Responses to COVID-19 mRNA Vaccine within First Three Months (preprint)

Background: Although the SARS-CoV-2 mRNA vaccines have proven high efficacy, limited data exists on the duration of immune responses and their relation to age and side effects.Methods: We studied the antibody and memory T cell responses to Spike protein after the two-dose Comirnaty mRNA vaccine in 122 volunteers up to 3 months and correlated the findings with age and side effects.Findings: We found a robust antibody response after the second vaccination dose. However, the antibody levels declined at 6 and 12 weeks postvaccination, indicating a waning of the immune response. Regardless, the average levels remained higher compared to pre-vaccination or in COVID-19 convalescent individuals. The antibodies efficiently blocked ACE2 receptor binding to Spike protein of four variants of concern at one week but this was decreased at three months, in particular with B.1.351 and P1 isolates. 87% of individuals developed Spike-specific memory T cell responses, which were lower in individuals with increased proportions of immunosenescent CD8+ TEMRA cells. We found a decreased vaccination efficacy but fewer adverse events in older individuals, suggesting a detrimental impact of age on outcome.Interpretation: The mRNA vaccine induces a strong antibody response to four variants at 1 week postvaccination but decreases thereafter, in particular among older individuals. T cell responses, although detectable in the majority, were lower in individuals with immunosenescence. The deterioration of vaccine response needs to be monitored to define the optimal time for the revaccination. Funding: The Estonian Research Council, Icosagen Cell Factory, and SYNLAB Estonia.Declaration of Interests: None to declare. Ethics Approval Statement: The study has been approved by the Research Ethics Committee of the University of Tartu on February 15, 2021 (No 335/T-21). Patients signed informed consent before recruitment into the study.

Declined antibody responses to COVID-19 mRNA vaccine within first three months (preprint)

Background Although the SARS-CoV-2 mRNA vaccines have proven high efficacy, limited data exists on the duration of immune responses and their relation to age and side effects. Methods We studied the antibody and memory T cell responses to Spike protein after the two-dose Comirnaty mRNA vaccine in 122 volunteers up to 3 months and correlated the findings with age and side effects. Findings We found a robust antibody response after the second vaccination dose. However, the antibody levels declined at 6 and 12 weeks postvaccination, indicating a waning of the immune response. Regardless, the average levels remained higher compared to pre-vaccination or in COVID-19 convalescent individuals. The antibodies efficiently blocked ACE2 receptor binding to Spike protein of four variants of concern at one week but this was decreased at three months, in particular with B.1.351 and P1 isolates. 87% of individuals developed Spike-specific memory T cell responses, which were lower in individuals with increased proportions of immunosenescent CD8+ TEMRA cells. We found a decreased vaccination efficacy but fewer adverse events in older individuals, suggesting a detrimental impact of age on outcome. Interpretation The mRNA vaccine induces a strong antibody response to four variants at 1 week postvaccination but decreases thereafter, in particular among older individuals. T cell responses, although detectable in the majority, were lower in individuals with immunosenescence. The deterioration of vaccine response needs to be monitored to define the optimal time for the revaccination. Funding The Estonian Research Council, Icosagen Cell Factory, and SYNLAB Estonia. Research in context Evidence before this study The first studies addressing the immune responses in older individuals after the administration of 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 May 20th, 2021. To date, most mRNA vaccine response studies have not been peer-reviewed, and data on the dynamics of antibody response, role of age 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 one to two weeks) after the first dose but little longer-term evidence exists on the postvaccination antibody persistence. Added value of this study In this study, we assessed the antibody response up to three months after the full vaccination with Pfizer-BioNTech Comirnaty mRNA vaccine in 122 individuals. Our findings show strong Spike RBD antibody responses one week after the second dose with the capacity to block ACE2-Spike protein interaction, however, the antibodies declined significantly at three months after the second dose. The inhibition of ACE2-Spike interaction was weaker with South African (B.1.351) and Brazilian (P.1) than with Wuhan and UK (B.1.1.7) SARS-CoV-2 isolates. At three months 87% of vaccinated individuals developed either CD4+ or CD8+ T cell responses. Those negative for Spike-specific T cell response also tended to have lower Spike-specific antibody levels. In addition, CD4+ T cell response was decreased among vaccinated individuals with elevated levels of senescent CD8+ TEMRA cells. We found a weaker antibody response and faster waning of antibodies in older vaccinated individuals, which correlated with fewer side effects at the time of vaccinations. Implications of all the available evidence Our results show that two doses of Pfizer-BioNTech Comirnaty mRNA vaccine induce a strong antibody and T cell responses to Spike RBD region but the antibody levels are declined at three months after the second dose. Nevertheless, even at three months, the anti-Spike RBD antibody levels stay significantly higher than at prevaccination, after the first dose of vaccine, or in Covid-19 postinfection. Our findings implicate older individuals to have fewer vaccination adverse effects and weaker immune response after the vaccination and point to the need for more individualized vaccination protocols, in particular among older people.