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Full COVID-19 vaccination boosts antibody response in those with prior infection

Among those with a prior infection, full COVID-19 vaccination boosts their antibody response even to variants of concern.

Vaccines against COVID-19 have been administered across the globe and have been shown to be efficacious at preventing COVID-19 illness. However, with the emergence of viral variants, some of which are able to escape neutralising antibodies, there is an increased risk of vaccine breakthrough infections. While it is possible to modify existing vaccines to ensure that they are effective against variants of concern, an alternative strategy is to provide individuals with a third, or booster vaccination dose. In fact, there is animal data to suggest that a booster dose increases antibody titres to at least one variant of concern although whether this strategy will be effective in humans remains uncertain. One way of studying the value of a booster dose, is to compare the antibody response generated after full vaccination among those with and without prior infection. This was the objective of a study by a team from the Wolfson Centre for Global Virus Research, University of Nottingham, UK. They used data from the PANTHER Study which is designed to track frontline healthcare workers. For the present study, the researchers were interested in any differences in the antibody response among fully vaccinated individuals, in those with or without a prior COVID-19 infection. Participants were split into two groups (prior or no prior infection) and blood samples taken for analysis of IgG antibody levels to the wild-type COVID-19 and against two variants of concern, B.1.351 and P1 after both their first and second doses of vaccine which were given 10 weeks apart.

The total cohort consisted of 45 individuals with a mean age of 47.5 years (80% female) and 20 with a prior infection, all of whom had received two doses of BNT162b. The level of antibodies among individuals with a prior infection were higher after a single vaccine dose compared to previously uninfected participants. Interestingly, after the second vaccine dose, there was a significantly increased antibody response, not just to the wild-type COVID-19, but to the two variants of concern among those who had a prior infection compared with uninfected individuals.

Commenting on these findings, the authors suggested that their data showed how repeated exposure to COVID-19, i.e., through a prior infection and two doses of a vaccine, increased the level of neutralising antibodies. In other words, a prior infection much like a booster dose. Furthermore, it was also apparent that this increased antigenic exposure appeared to broaden an individual’s antibody response by creating neutralising antibodies to the two variants of concern. If confirmed in future studies, these results would be of enormous importance. For instance, if repeated exposure not only enhanced but extended immunity against variants of concern, there is a very strong argument for giving individuals a further, third, booster vaccine dose, even if this is directed at the original spike protein, to combat any new variants likely to emerge in the future.

Urbanowicz RA et al. Two doses of the SARS-CoV-2 BNT162b2 vaccine enhances antibody responses to variants in individuals with prior SARS-CoV-2 infection. Sci Transl Med 2021