Book review
https://doi.org/10.3325/cmj.2021.62.630
Waning immunity six months after BioNTech/Pfizer COVID19 vaccination among nursing home residents in Zagreb, Croatia
Branko Kolarić
; Andrija Štampar Teaching Institute of Public Health, Zagreb, Croatia
Andreja Ambriović-Ristov
; Ruđer Bošković Institute, Zagreb, Croatia
Irena Tabain
; Croatian Institute of Public Health, Zagreb, Croatia
Tatjana Vilibić Čavlek
; Croatian Institute of Public Health, Zagreb, Croatia
Abstract
Aim To assess the humoral immunity to COVID-19 in nursing home residents six months after vaccination.
Methods This seroepidemiological research enrolled 118
residents of one nursing home in Zagreb. All participants
received two doses of BioNTech/Pfizer COVID-19 and had
no previously detected SARS-CoV-2 infection. The samples
were tested for the presence of neutralizing antibodies using a virus neutralization test. A SARS-CoV-2 strain isolated
in Vero E6 cells from a Croatian COVID-19 patient was used
as a stock virus. Neutralizing antibody titer was defined as
the reciprocal of the highest serum dilution that showed at
least 50% neutralization. Neutralizing antibody titer ≥8 was
considered positive.
Results Sixty-four (54%) participants had a positive neutralizing antibody titer, 27 (23%) had a low positive titer (titer 8), and 27 (23%) had a negative titer. Women had a significantly higher median titer than men (16 [interquartile
range, IQR 24] vs 8 [IQR 12], Mann-Whitney U=1033,
P=0.003). Age was negatively but not significantly correlated with neutralizing antibody titer (Spearman’s rho
-0.132, P=0.155).
Conclusion Almost half of the participants (46%) had a
negative or low positive titer six months after having been
fully vaccinated. This study suggests that humoral immunity among nursing home residents considerably wanes six
months after BioNTech/Pfizer COVID-19 vaccination. Our
results could contribute to the discussion about the need
for a booster dose.
Keywords
Hrčak ID:
278874
URI
Publication date:
23.12.2021.
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