• Einav G Levin, Yaniv Lustig, Carmit Cohen, Ronen Fluss, Victoria Indenbaum, Sharon Amit, Ram Doolman, Keren Asraf, Ella Mendelson, Arnona Ziv, Carmit Rubin, Laurence Freedman, Yitshak Kreiss, and Gili Regev-Yochay.
• From the Infection Prevention and Control Unit (E.G.L., C.C., G.R.-Y.), the Biostatistics and Biomathematics Unit, Gertner Institute of Epidemiology and Health Policy Research (R.F., A.Z., C.R., L.F.), the Automated Mega-Laboratory, Laboratory Division (R.D., K.A.), the Department of Clinical Microbiology (S.A.), and the Sheba Medical Center Management (Y.K.), Sheba Medical Center Tel Hashomer, and the Central Virology Laboratory, Public Health Services, Ministry of Health (Y.L., V.I., E.M.), Ramat Gan, and the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv (E.G.L., Y.L., E.M., Y.K., G.R.-Y.) - all in Israel.
• N. Engl. J. Med. 2021 Dec 9; 385 (24): e84e84.

BackgroundDespite high vaccine coverage and effectiveness, the incidence of symptomatic infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been increasing in Israel. Whether the increasing incidence of infection is due to waning immunity after the receipt of two doses of the BNT162b2 vaccine is unclear.MethodsWe conducted a 6-month longitudinal prospective study involving vaccinated health care workers who were tested monthly for the presence of anti-spike IgG and neutralizing antibodies. Linear mixed models were used to assess the dynamics of antibody levels and to determine predictors of antibody levels at 6 months.ResultsThe study included 4868 participants, with 3808 being included in the linear mixed-model analyses. The level of IgG antibodies decreased at a consistent rate, whereas the neutralizing antibody level decreased rapidly for the first 3 months with a relatively slow decrease thereafter. Although IgG antibody levels were highly correlated with neutralizing antibody titers (Spearman's rank correlation between 0.68 and 0.75), the regression relationship between the IgG and neutralizing antibody levels depended on the time since receipt of the second vaccine dose. Six months after receipt of the second dose, neutralizing antibody titers were substantially lower among men than among women (ratio of means, 0.64; 95% confidence interval [CI], 0.55 to 0.75), lower among persons 65 years of age or older than among those 18 to less than 45 years of age (ratio of means, 0.58; 95% CI, 0.48 to 0.70), and lower among participants with immunosuppression than among those without immunosuppression (ratio of means, 0.30; 95% CI, 0.20 to 0.46).ConclusionsSix months after receipt of the second dose of the BNT162b2 vaccine, humoral response was substantially decreased, especially among men, among persons 65 years of age or older, and among persons with immunosuppression.Copyright © 2021 Massachusetts Medical Society.

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