Single dose of Pfizer vaccine offers robust protection for those who have had COVID-19, studies find

Two British studies published this week indicate that COVID-19 survivors, who have antibodies against the virus, need only a single dose of the Pfizer vaccine to fend off re-infection. “This could potentially accelerate vaccine rollout,” wrote the authors of one of the papers published in The Lancet. “Wider coverage without compromising vaccine-induced immunity could help reduce variant emergence.” The team from University College London and Public Health England tracked 51 health workers, one-half of whom had been infected. One dose of the vaccine, they found, boosted antibody levels by more than 140 times their peak levels before immunization and appeared to offer them better protection against the virus than what never-infected individuals got from receiving two doses. Scientists at Imperial College London, meanwhile, followed 72 health workers who received vaccinations in late December. About one-third of those participants presented evidence of earlier infection, and researchers documented their “very strong” antibody and other immune system responses to a single dose of the Pfizer vaccine. While the studies support the concept of administering just one injection to people already carrying coronavirus antibodies, it remains to be seen how durable the post-vaccine immune response is.