As Covid-19 infections rise in England, people are increasingly reporting contracting Sars-CoV-2 for the second or even third time.
A new analysis has suggested that unvaccinated people should expect to be reinfected with Covid-19 every 16 months, on average.
Now that winter is approaching, scientists warn that such reinfections 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 level of prevalence and frequent exposure to the virus, such as in schools, you will see that more and more people are reinfected despite being double vaccinated,” said Stephen Griffin, associate professor of virology. at the University of Leeds.
At this time last year, it was assumed that although reinfections could occur, this was relatively uncommon, 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 has further complicated the situation.
“Certainly, in the healthcare workers that we have been studying, there are many people who had moderately decent levels of antibodies who have been, in some cases, previously infected and vaccinated with double doses, who have contracted symptomatic infections,” he 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.”
OUR DATA published on October 6 says that among 20,262 Britons who tested positive for Covid-19 between July 2020 and September 2021, there were 296 reinfections, defined as a new positive test 120 days or more after a first initial positive test, with a average (median) time of 203 days between positive tests.
However, the risk of reinfection appears to have been higher since May 2021 when Delta took office as the predominant variant.
More data from the US, where multiple states have started tracking and reporting reinfection rates, supports the idea that there is a substantially increased risk of reinfection with Delta.
On Oklahoma, which has a population of about 3.9 million, 5,229 reinfections were reported during September (equivalent to a reinfection rate of 1,152 per 100,000) and reinfections have increased 350% since May.
The U.S. Centers for Disease Control and Prevention (CDC) defines reinfection as a laboratory-confirmed case of Covid-19 that occurs 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 increasing levels of Sars-CoV-2 infections in the UK, many of us know personally the children and adults who were reinfected. , sometimes after a relatively short period from your first infection.
“We still don’t know much about risk factors for reinfection, but the theoretical assumption that once all young people contract it, the pandemic will end is increasingly unlikely.”
To help answer this question, Professor Jeffrey Townsend and colleagues at Yale University School of Medicine analyzed known immunological and reinfection data from other coronaviruses, including those that cause Sars, MERS, and common colds.
By combining this with antibodies and other immunological data from people who had recovered from Sars-CoV-2, they were able to model the risk of Covid-19 reinfection over time.
The research, published in The lancet microbe, suggested that reinfections would become increasingly common as immunity waned, particularly when the number of infections was high.
“If we had no infection controls, no one was masking or socially distancing, there were no vaccines, we should expect a reinfection within 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 are suppressing the level of infections, the UK reported 49,156 Covid cases on Monday, the highest number since mid-July. Rates are highest among high school students, with 8.1% of this group believed to have had Covid-19 in the week ending October 9.
“If you allow it to go crazy in any age group, then it will go crazy in all age groups,” Townsend said.
“The main implications are that if you haven’t been vaccinated, you should get vaccinated, and if you have been infected, you should go ahead and get vaccinated anyway, because that will extend the duration of your protection.”
Griffin said, “If you don’t repress the prevalence [in schoolchildren], you will contract the spread of infection and possibly reinfection, which will then potentially spread to parents whose vaccinations may be declining and, more critically, to grandparents and clinically vulnerable individuals. “
George is Digismak’s reported cum editor with 13 years of experience in Journalism