Age-dependent Immune Response to the Biontech/Pfizer BNT162b2 Coronavirus Disease 2019 Vaccination

Background. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has led to the development of various vaccines. Real-life data on immune responses elicited in the most vulnerable group of vaccinees older than age 80 years old are still underrepresented despite the prioritization of the elderly in vaccination campaigns. Methods. We conducted a cohort study with 2 age groups, young vaccinees below the age of 60 years and elderly vaccinees over the age of 80 years, to compare their antibody responses to the first and second dose of the BNT162b2 coronavirus disease 2019 vaccination. Results. Although the majority of participants in both groups produced specific immunoglobulin G antibody titers against SARS-CoV-2 spike protein, titers were significantly lower in elderly participants. Although the increment of antibody levels after the second immunization was higher in elderly participants, the absolute mean titer of this group remained lower than the <60 years of age group. After the second vaccination, 31.3% of the elderly had no detectable neutralizing antibodies in contrast to the younger group, in which only 2.2% had no detectable neutralizing antibodies. Conclusions. Our data showed differences between the antibody responses raised after the first and second BNT162b2 vaccination, in particular lower frequencies of neutralizing antibodies in the elderly group. This suggests that this population needs to be closely monitored and may require earlier revaccination and/or an increased vaccine dose to ensure stronger long-lasting immunity and protection against infection.