Without Covid-19 jab, “reinfection can occur every 16 months”

Without Covid-19 jab, “reinfection can occur every 16 months”

As Covid-19 infections increase in England, more and more people are reporting catching Sars-CoV-2 for a second or even a third time.

A new analysis has suggested that unvaccinated people should expect to be re-infected with Covid-19 every 16 months, on average.

As winter approaches, scientists warn such re-infections could increase the burden on the NHS, with some calling for the vaccination program to be extended to all schoolchildren, including two doses for adolescents.

“If you have a high prevalence and frequent exposure to the virus, like in schools, you are going to see more and more people reinfect themselves despite having been doubly vaccinated,” said Stephen Griffin, associate professor of virology. at the University of Leeds.

Around the same time last year, the hypothesis was that although re-infections could occur, it was relatively rare, with only about two dozen recorded worldwide.

We now know that natural immunity to Sars-CoV-2 begins to wane over time. A Danish study suggested that those under 65 had around 80% protection for at least six months, while those over 65 had only 47% protection.

The arrival of the Delta variant further complicated the situation.

“Certainly among the healthcare workers we studied there are a lot of people who had moderately decent antibody levels who were, in some cases, previously infected and vaccinated at double doses, who contracted symptomatic infections. Said Danny Altmann, professor of immunology at Imperial College London.

“I think it’s a lot more common than the types of numbers we were used to before. “

ONS data released on October 6 indicates that among 20,262 Britons who tested positive for Covid-19 between July 2020 and September 2021, there were 296 re-infections – defined as a new positive test 120 days or more after a first test initial positive – with an average (median) delay of 203 days between positive tests.

However, the risk of re-infection appears to have been higher since May 2021, when Delta took over as the predominant variant.

Other data from the United States, where various states have now started tracking and reporting reinfection rates, support the idea that there is a significantly higher risk of reinfection with Delta.

In Oklahoma, which has a population of approximately 3.9 million, 5,229 re-infections were reported in September (equivalent to a re-infection rate of 1,152 per 100,000) and re-infections have increased 350% since May.

The United States Centers for Disease Control and Prevention (CDC) defines reinfection as a laboratory confirmed case of Covid-19 occurring 90 days or more after a previously laboratory confirmed case.

Dr Nisreen Alwan, Associate Professor of Public Health at the University of Southampton, said: ‘With the increasing levels of Sars-CoV-2 infections in the UK, many of us are personally aware of children. and adults who have been re-infected, sometimes after a relatively short period from their first infection.

“We still don’t know much about the risk factors for re-infection, but the theoretical assumption that once all young people get it, the pandemic is over is becoming increasingly unlikely. “

To help answer this question, Professor Jeffrey Townsend and colleagues at Yale University School of Medicine analyzed known reinfection and immunologic data from other coronaviruses, including those that cause Sars, MERS and the common cold.

By combining this with antibodies and other immunologic data from people who had recovered from Sars-CoV-2, they were able to model the risk of re-infection from Covid-19 over time.

The research, published in The Lancet Microbe, suggested that re-infections would become more common as immunity wanes, especially when the number of infections is high.

“If we had no infection control, no one masked or socially distanced themselves, there were no vaccines, we should expect re-infection over a period of three months to five years – which means that the average person should expect to receive Covid every three months for five years, ”Townsend said.

Although vaccines suppress the level of infections, the UK reported 49,156 cases of Covid on Monday, the highest figure since mid-July. Rates are highest among high school students, with around 8.1% of this group believed to have had Covid-19 in the week ending October 9.

“If you allow him to go wild in any age group, then he goes wild in all age groups,” Townsend said.

“The main implications are that if you haven’t been vaccinated you should get the shot, and if you’ve been infected you should still get the shot because that will prolong the duration of your protection. “

Griffin said, “If you don’t suppress the prevalence [in schoolchildren], you will get the infection to spread and possibly re-infection, which will then potentially spread to parents whose vaccines may be declining, and more severely to grandparents and clinically vulnerable people. “


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