People who have received both doses of a coronavirus vaccine are half as likely to be infected with Covid-19, a new study has found.
Researchers behind the React trial, which tracked the disease throughout the pandemic, said that even though people with a double bite come into contact with someone with Covid-19, only one in 25 (3.84%) will catch it on her own. .
And cases are generally milder in people with a double bite who are infected, they added.
Researchers at Imperial College London said it was uncertain whether or not there would be an increase in infections in September when schools return and there will be more socialization inside.
But they stressed that each additional person who gets the vaccine “takes away a good deal of the potential transmission of what may or may not happen in September.”
The study draws information and swab samples from over 98,000 randomly selected people across England.
The percentage of those who tested positive for Covid-19 was 0.4% among those who were double stung compared to 1.21% among those unvaccinated – a triple difference.
After adjusting for various factors, they found that the vaccine’s effectiveness was 49% in people who reported receiving a double injection.
“In other words, people who are doubly vaccinated are half as likely to be infected,” said Professor Paul Elliott, director of the React program and president of epidemiology and public health medicine at Imperial College. from London.
A previous study by Public Health England found higher efficacy rates, but Professor Elliot said this was because PHE research relied on data mainly from symptomatic individuals.
The React study relies on data for people with and without symptoms in the general population.
When the authors looked at data from symptomatic individuals only, the efficacy rates were higher – 59%.
Of those studied, 40% of people were found to have Covid-19 but had no symptoms – a figure that varied slightly over the course of the study.
Professor Elliott added: ‘Our estimates are a little lower than what Public Health England showed – remember they were focused on routine testing of people, so almost all of them would be symptomatic, and we are looking at the effectiveness. in a random sample of the general population, which includes asymptomatic individuals.
He said those who were vaccinated were likely to have less serious infections, with double-vaccinated people having a lower viral load than those who were infected after a single dose or were unvaccinated.
“Vaccination is very effective against serious results,” said Professor Elliott.
But he added: “There are people who are doubly vaccinated who will be infected because even with very high protection, it is not 100%.”
The researchers found that about 44% of the infections were in people who had been vaccinated, but warned: “As a higher proportion of the population is vaccinated, the proportion of infections in this group may increase.”
Steven Riley, professor of infectious disease dynamics at the Imperial, said young people were the driving force behind infection rates before the recent drop in cases, adding: “So every additional person who gets vaccinated takes a decent share of the potential transmission of what may or may not happen in September.
âThere has been a drop, a plateau now, and I think it’s hard to forecast over the summer months. There is uncertainty as to what could happen in September when schools return and increase the indoor mix. “
The study found that the Delta variant had “completely taken over” from the Alpha variant, with 100% of the swabs provided showing that people were infected with the newer variant.
Commenting on the study, Health Secretary Sajid Javid said: âOur vaccination deployment is building a wall of defense which means we can carefully loosen restrictions and get back to the things we love, but we have to be careful then. that we learn to live with it. virus.
âToday’s report shows the importance of taking personal responsibility by isolating yourself if you are contacted, getting tested for symptoms and wearing face coverings where appropriate.
“I urge anyone who has not yet received a vaccine to get bitten and take both doses – the vaccines are safe and they work.”