If you are planning to avoid vaccination just because you are a Covid survivor, think twice. According to a new study, despite a prior Covid-19 infection young people can likely catch the virus again and may still transmit it to others.
Even after a previous infection and the presence of antibodies, vaccination is still necessary to boost immune responses, prevent reinfection, reduce transmission, and that young person should take up the vaccine wherever possible, asserts the study published in the journal The Lancet Respiratory Medicine.
"Immunity is not guaranteed by past infection, and vaccinations that provide additional protection are still needed for those who have had Covid-19," said Professor Stuart Sealfon, from the Icahn School of Medicine at Mount Sinai, the US.
In the study, the team involved 2,346 young and fit Marines from the US Marine Corps – 189 were seropositive (they had previously been infected with SARS-CoV-2 and had antibodies) and 2,247 were seronegative at the start of the study.
Across both groups of recruits, there were 1,098 (45 percent) new infections between May and November 2020. Among the seropositive participants, 19 (10 percent) tested positive for a second infection during the study. Of the recruits who were seronegative, 1,079 (48 percent) became infected during the study.
Further, they found that, among the seropositive group, participants who became reinfected had lower antibody levels against the SARS-CoV-2 virus than those who did not become reinfected. The neutralising antibodies were also less common – in 45 (83 percent) of 54 uninfected, and in six (32 percent) of 19 reinfected participants.
In addition, they found the viral load (the amount of measurable SARS-CoV-2 virus) in reinfected seropositive recruits was on average only 10 times lower than in infected seronegative participants, which could mean that some reinfected individuals could still have a capacity to transmit infection. However, this needs further investigation, the team said.