Investigators found that a single initial dose may be sufficient for patients with prior infection.
COVID-19 vaccine booster shots may be necessary for everyone, according to a study published in ACS Nano. Further, the study supports existing evidence that patients who had COVID-19 prior to being vaccinated need only 1 vaccine dose.
Both the Pfizer-BioNTech and Moderna vaccines trigger the spike protein receptor binding domain (RBD), and clinical trials demonstrated that these vaccines were approximately 95% effective in preventing symptomatic infections after 2 doses. However, these trials did not include a large number of individuals with prior COVID-19 infection and as a result, the immune response of this population is not as well-established. Further, the length of time for which virus-neutralizing antibodies persist, as well as the time course of antibody development, were not clearly characterized. The investigators intended this current study to compare antibody levels, quality, and persistence after 1 and 2 doses of mRNA vaccine in people with or without prior SARS-CoV-2 infection.
The researchers used an enzyme-linked immunosorbent assay to measure antibodies against RBD in patients who received the Pfizer-BioNTech or Moderna vaccine as well as unvaccinated individuals briefly after their recovery from mild or severe cases of COVID-19. In the 28 patients who were not previously infected, 1 vaccine dose triggered antibody levels comparable to those seen after mild COVID-19 infections, regardless of which vaccine they received. A second dose was necessary in these patients to obtain anti-RBD antibodies approaching those observed after severe cases. However, for the 36 participants who had COVID-19 prior to vaccination, the first dose produced a considerable antibody response similar to severe natural infection, whereas the second dose provided no additional increase in antibody levels.
The quality of antibodies followed a similar pattern in these 2 groups. Quality, measured by the antibodies’ ability to neutralize the SARS-CoV-2 spike protein and their potency, waned in both groups at a rate similar to natural infection. This resulted in an average potency loss of 90% within 85 days. According to the researchers, this suggests that booster vaccinations will likely be required for everyone, but further research on T cell responses to the vaccines is needed in order to reach a definitive answer.
Had COVID-19? One vaccine dose enough; boosters for all, study says [news release]. EurekAlert; June 23, 2021. Accessed June 23, 2021. https://www.eurekalert.org/pub_releases/2021-06/acs-hco061821.php