Around half of people over 80 years of age require a second dose of the Pfizer-BioNTech SARS-CoV-2 mRNA-based vaccine in order to achieve maximum virus neutralization, a Nature study involving 140 participants suggests. The findings have important implications for the roll-out of the global vaccine program.
Ravindra Gupta and colleagues compared the post-vaccination immune response in 80 elderly people and 60 younger healthcare workers. Three weeks after the first dose of the Pfizer-BioNTech vaccine, a lower proportion of participants over the age of 80 achieved adequate neutralization titres compared to those in the younger group. Elderly participants were also less able to neutralize variants of concern, such as the Alpha (B.1.1.7) and Beta (B.1.351) variants, compared to younger participants following a first dose. After the second dose, however, neutralizing antibody responses were comparable in all participants.
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