Those infected with the SARS-CoV-2 coronavirus have an 88% lower risk of hospitalization or death from Covid-19 for at least 10 months than those who do not acquire this natural immunity, indicates a study released today.
The researchers specify, on the other hand, that the infections with pre-Omicron variants provided a “substantially reduced” natural immunity against reinfection with the Omicron BA.1 strain, in which 10 months after the first infection the protection was only 36%.
The work published this Friday in the scientific journal The Lancet constitutes the “most complete” analysis carried out to date on the level of protection and scope of this after being infected by different variants of that virus, although it does not include data on infection by the virus. virus. Omicron XBB variant and its underlines.
65 studies from 19 countries were reviewed and analyzed, comparing “the reduction in the risk of Covid-19 between unvaccinated individuals against reinfection by SARS-CoV-2 and unvaccinated individuals without prior infection up to September 2022,” says a dissemination statement. of the studio.
According to the research, the level and duration of immunity “against reinfection, symptomatic disease, and severe disease” are at least equal to that provided by two doses of mRNA vaccines (Moderna, Pfizer-BioNtech) for Alpha, Delta and Omicron BA.1.
“Vaccination is the surest way to achieve immunity, whereas achieving natural immunity (through contagion) must be weighed against the risks of severe illness and death associated with initial infection,” says Stephen Lim of the Metrics Institute. and Health Assessment (IHME). ) from the University of Washington School of Medicine, in the United States, lead author of the analysis, cited in the statement.
Caroline Stein, also from IHME and a co-author of the study, points out that “vaccines are still important for everyone” to protect both high-risk populations, such as those over 60, as well as those already suffering from other diseases.
“This also includes populations that were not previously infected and unvaccinated groups, as well as those that were infected or received the last dose of the vaccine more than six months ago,” he adds, arguing that natural immunity and the situation in relation to the vaccination must be taken into account to “get a complete picture of an individual’s immunity profile”.
Since January 2021, several studies have been published on the effectiveness of SARS-CoV-2 infection in reducing the risk of reinfection and how immunity wanes over time, but none comprehensively assessed how long protection would last after natural infection against different variants. .
Analysis of data from 21 studies on infection with a pre-Omicron variant “estimated that protection against reinfection with a pre-Omicron variant was around 85% in the first month and decreased to around 79% after at 10 months,” while the natural immunity achieved with “a pre-Omicron variant infection versus an Omicron BA.1 variant reinfection was lower (74% at month) and declined more rapidly to 36% at 10 months.” months”.
“However, analysis of five studies reporting severe illness (hospitalization and death) revealed that protection (at this level) remained universally high over 10 months: 90% for alpha and delta ancestors and 88% for Omicron BA. 1”.
Six other studies evaluating protection specifically against the Omicron variant sublines (BA.2 and BA.4/BA.5) indicated that protection was significantly less when the previous infection was of a pre-Omicron variant, but that it was still “a higher level when the previous infection was due to the Omicron strain, according to the study published today by The Lancet.
According to another of the co-authors of the study, Hasan Nassereldine, from the IHME, the lower protection against infections with the ancestral strains in relation to the Omicron variant and its sublines reflects the mutations that have occurred and that allow them to “escape more easily from acquired immunity”. . than other variants”.
“The limited data we have on the natural immunity protection of the Omicron variant and its sublines underscore the importance of continued evaluation, particularly as they are estimated to have infected 46% of the population worldwide between November 2021 and June 2022”, he says. the scientist, adding that more research is also needed to “assess the natural immunity of emerging variants and analyze the protection provided by combinations of vaccination and natural infection.”
The authors of the study “Protection of SARS-CoV-2 infection against reinfection: a systematic review and meta-analysis” point out that the work has some limitations, since the data on the Omicron BA.1 variant and its sublines are also limited. like the situation in Africa.
They add that estimates of protection may also have been influenced by limited data available beyond 10 months after initial infection, as well as different or incomplete information being recorded, for example, on previous infection or hospitalizations. .
Since June 1, 2022, it is estimated that the Covid-19 pandemic has caused 17.2 million deaths (of which 6.88 million were registered) and 7.630 million infections and reinfections, according to the study, which It adds that “a large proportion of these infections occurred after November 14, 2022.”
“The immunity conferred by infections should be weighed against the protection gained by vaccination when assessing the future burden of COVID-19, providing guidance on when individuals should be vaccinated and on policies that make vaccination mandatory for workers or restrict access to places where the risk of transmission is high (…), depending on the immunological status”.
The European Medicines Agency (EMA) defended this Wednesday the annual vaccination against Covid-19, warning that the disease “still represents a significant burden” for health systems in Europe.
Autumn, “the beginning of the cold season”, was considered the best time to administer the vaccine against Covid-19, coinciding with the time of inoculation of vaccines against other respiratory viruses (such as influenza).
At the end of January, the World Health Organization (WHO) announced that its Emergency Committee on International Regulations had decided to maintain the maximum alert level for the Covid-19 pandemic.
While the committee acknowledged that the pandemic may be approaching a tipping point, it decided that there is “no doubt” that the SARS-CoV-2 coronavirus will remain a permanently established pathogen in humans and animals in the future and, therefore long term. Long-term public health action is urgently needed, the WHO said in a statement.
Covid-19 is a pandemic infectious respiratory disease caused by the SARS-CoV-2 coronavirus, a type of virus that was detected three years ago in China, spreading rapidly throughout the world, and has assumed several variants and subvariants, some more contagious. . What others.
In Portugal, vaccination against Covid-19 began on December 27, 2020, and since then, primary doses and booster doses have been administered in stages.
Source: TSF
