Durability and determinants of anti-SARS-CoV-2 spike antibodies following the second and third doses of mRNA COVID-19 vaccine

BackgroundEpidemiological data regarding differences in durability and its determinants of humoral immunity following 2- and 3-dose COVID-19 vaccination are scarce. MethodsWe repeatedly assessed the anti-spike IgG antibody titers of 2- and 3-dose mRNA vaccine recipients among the staff of a medical and research center in Tokyo. Linear mixed models were used to estimate trajectories of antibody titers from 14 to 180 days after the last immune-conferred event (vaccination or infection) and compare antibody waning rates across prior infection and vaccination status, and across background factors in infection-naive participants. ResultsA total of 6901 measurements from 2964 participants (median age, 35 years; 30% male) were analyzed. Antibody waning rate (per 30 days [95% CI]) was slower after 3-dose (25% [23-26]) than 2-dose (36% [35-37]). Participants with hybrid immunity (vaccination and infection) had further slower waning rates: 2-dose plus infection (16% [9-22]); 3-dose plus infection (21% [17-25]). Older age, male sex, obesity, coexisting diseases, immunosuppressant use, smoking, and alcohol drinking were associated with lower antibody titers, whereas these associations disappeared after 3-dose, except for sex (lower in female participants) and immunosuppressant use. Antibody waning was faster in older participants, females, and alcohol drinkers after 2-dose, whereas it did not differ after 3-dose across except sex. ConclusionsThe 3-dose mRNA vaccine conferred higher durable antibody titers, and previous infection further enhanced its durability. The antibody levels at a given time point and waning speed after 2-dose differed across background factors; however, these differences mostly diminished after 3-dose.

Neutralizing antibodies following three doses of BNT162b2 vaccine, breakthrough infection, and symptoms during the Omicron predominant wave

BackgroundData on the role of immunogenicity following the third vaccine dose against Omicron infection and coronavirus disease 2019 (COVID-19)-compatible symptoms of infection are limited. MethodsFirst we examined vaccine effectiveness (VE) of the third-dose against the second dose during the Omicron wave among the staff at a tertiary hospital in Tokyo. In a case-control study of a cohort of third vaccine recipients, we compared the pre-infection levels of live-virus neutralizing antibodies (NAb) against Omicron between breakthrough cases and their controls, who had close contact with COVID-19 patients. Among these cases, we examined the association between pre-infection NAb levels and the number of COVID-19-compatible symptoms experienced during the Omicron wave. ResultsAmong the 1456 participants for VE analysis, 60 (4%) breakthrough infections occurred during the Omicron wave (January to March 2022). The third-dose VE for infection, relative to the second dose was 54.6% (95% CI: 14.0-76.0). Among the recipients of the third vaccine, pre-infection NAb levels against Omicron did not significantly differ between the cases and controls. Among the cases, those who experienced COVID-19-compatible symptoms had lower pre-infection NAb levels against Omicron than those who did not. ConclusionsThe third vaccine dose was effective in decreasing the risk of severe acute respiratory syndrome coronavirus 2 infection during the Omicron wave compared with the second dose. Among third-dose recipients, higher pre-infection NAb levels may not be associated with a lower risk of Omicron infection. Contrarily, they may be associated with fewer symptoms of infection. SummaryThe third vaccine dose reduced SARS-CoV-2 infection risk during the Omicron wave. Higher neutralizing antibody levels may not reduce Omicron infection risk in third-dose patients. On the contrary, it may be associated with fewer symptoms of infection.

COVID-19 breakthrough infections and pre-infection neutralizing antibody

BackgroundWhile increasing coverage of effective vaccines against coronavirus disease 2019 (COVID-19), emergent variants raise concerns about breakthrough infections. Data are limited, however, whether breakthrough infection during the epidemic of the variant is ascribed to insufficient vaccine-induced immunogenicity. MethodsWe described incident COVID-19 in relation to the vaccination program among workers of a referral hospital in Tokyo. During the predominantly Delta epidemic, we followed 2,473 fully vaccinated staff (BNT162b2) for breakthrough infection and selected three matched controls. We measured pre-infection neutralizing antibodies against the wild-type, Alpha (B.1.1.7), and Delta (B.1.617.2) strains using live viruses and anti-spike antibodies using quantitative assays, and compared them using the generalized estimating equation model between the two groups. ResultsNo COVID-19 cases occurred 1-2 months after the vaccination program during the fourth epidemic wave in Japan, dominated by the Alpha variant, while 22 cases emerged 2-4 months after the vaccination program during the fifth wave, dominated by the Delta variant. In the vaccinated cohort, all 17 cases of breakthrough infection were mild or asymptomatic and had returned to work early. There was no measurable difference between cases and controls in pre-infection neutralizing antibody titers against the wild-type, Alpha, and Delta, and anti-spike antibody titers, while neutralizing titers against the variants were considerably lower than those against the wild-type. ConclusionsPre-infection neutralizing antibody titers were not decreased among patients with breakthrough infection under the Delta variant rampage. The result points to the importance of infection control measures in the post-vaccination era, irrespective of immunogenicity profile.