Prior COVID-19 infection may reduce need for second jab

LONDON: People who have had COVID-19 may not need a second dose of vaccine, but are as much as three times more likely to develop serious side effects after receiving the first.
Data collected by King’s College London from 700,000 vaccinated people showed a link between prior infections and side effects, particularly among those who received the Pfizer jab.
It also suggested that a single dose proved just as effective as a double dose for those who had already been infected.
In total, 12.2 percent of recipients reported side effects, including muscle pain and headaches, after the Pfizer jab — rising to 35.7 percent of people who had previously had COVID-19.
For recipients of the Oxford / AstraZeneca vaccine, 31.9 percent reported side effects, rising to 52.7 percent in those previously infected.
Ellie Barnes, professor of hepatology and immunology at the University of Oxford, said this might be because the body’s immune system was already activated by prior infection.
“There’s emerging data to show that when you’ve had a COVID-19 infection your T cells become activated, and then over the weeks after that they become memory T cells and kind of calm down,” she added.
“But they are then able to respond very rapidly to subsequent vaccination, so if you’ve been infected before and then get your first dose of the vaccine, you have a really excellent response to that single dose compared to someone that wasn’t infected before.”
Researchers in Maryland and New York recently found that people with prior infection had more antibodies after their first vaccination than those who had never had the virus — as much as 10-20 times as many in the New York study — suggesting that second doses for previously infected people may be unnecessary. 
Eleanor Riley, professor of immunology and infectious disease at the University of Edinburgh, said: “Both US papers suggest that people who have had a PCR-confirmed COVID-19 infection may only require one dose of the vaccine.”
Lawrence Young, a virologist at the University of Warwick, said: “If future work can confirm this high level of immunity post a single mRNA vaccine in this group of individuals, this could become a viable option when there are concerns around vaccine supply.”