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, according to a study released this Thursday has been released.
In contrast, the researchers specify that infections with pre-Omicron variants produced “significantly reduced” natural immunity against re-infection with the Omicron strain BA.1., with protection only 36% 10 months after initial infection.
The work was published Thursday in the scientific journal The Lancet constitutes the “most comprehensive” analysis to date of the level and extent of protection after infection by different variants of that virus, although it does not include data on infection by the Omicron XBB variant and its sublines.
65 studies from 19 countries have been reviewed and analysed, comparing “the reduction in the risk of COVID-19 between unvaccinated individuals against re-infection by SARS-CoV-2 and unvaccinated individuals with no prior infection through September 2022” , a statement said. of the study.
According to the study, the level and duration of immunity “against re-infection, symptomatic disease and severe disease” are at least equivalent to two doses of mRNA vaccines (Moderna, Pfizer-BioNtech) for the Alpha, Delta and Omicron BA. 1.
“Vaccination is the safest way to achieve immunity, while achieving natural immunity (through contamination) must be weighed against the risks of serious illness and death associated with the initial infection.”said Stephen Lim, of the Institute for Health Metrics and Evaluation (IHME) at Washington University School of Medicine, in the United States, the lead author of the analysis, cited in the statement.
Caroline Stein, also from IHME and co-author of the study, points out “vaccines remain important for everyone” to protect both high-risk populations, such as the over-60s, and people who already have other diseases.
“This also includes previously uninfected and unvaccinated populations, as well as those who were infected or received the last vaccine dose more than six months ago.”he adds, arguing that natural immunity and the situation with regard to vaccination must be taken into account in order to “get a complete picture of an individual’s immunity profile”.
As of January 2021, several studies have been published on the effectiveness of SARS-CoV-2 infection in reducing the risk of reinfection and how immunity declines over time, but none have comprehensively assessed how long protection lasts after infection would persist. .
Analysis of data from 21 studies of infection with a pre-Omicron variant “estimated that the protection against reinfection of a pre-Omicron variant was approximately 85% in the first month and decreased to approximately 79% after 10 months”, while natural immunity achieved with “infection of the pre-Omicron variant versus re-infection of the Omicron BA.1 variant was lower (74% at one month) and declined more rapidly to 36% at approximately 10 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 the alpha and delta ancestors and 88% for Omicron BA. 1”.
A further six studies evaluating protection specifically against sublines of the Omicron variant (BA.2 and BA.4/BA.5) indicated that protection was significantly lower when the previous infection was from a pre-Omicron variant, but that it remained “a higher level” when the previous infection was due to the Omicron strain, according to the study released this Thursday by lancet.
According to another study co-author, Hasan Nassereldine, of 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 make them “easier to adapt to acquired immunity”. escape”. than other variants”.
“The limited data we have on the natural immune protection of the Omicron variant and its sublines underlines the importance of ongoing evaluation, especially as they are estimated to have infected 46% of the global population between November 2021 and June 2022.”says the scientist, adding that more research is also needed “to evaluate the natural immunity of emerging variants and analyze the protection afforded 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” note that the work has some limitations, as the data on the Omicron BA.1 variant and its sublines are also be limited. as the situation in Africa.
They add that the protection calculations may also have been affected by the limited data available more than 10 months after the initial infection, and by anomalous or incomplete information recorded, for example about a previous infection or hospital admissions.
According to the study, the Covid-19 pandemic has caused an estimated 17.2 million deaths (including 6.88 million recorded) and 7.63 billion (re)infections since June 1, 2022. took place after November 14, 2022″.
“The immunity conferred by infections should be weighed against the protection afforded by vaccination when assessing the future burden of COVID-19, providing guidance on when individuals should be vaccinated and on policies mandating vaccination for employees or restricted access to places where the risk of transmission is high (…), based on immune status”.
On Wednesday, the European Medicines Agency (EMA) defended the annual vaccination against Covid-19, warning that the disease “still represents a significant burden” on Europe’s health systems.
Autumn, “the beginning of the cold season”, was considered the best time to administer the vaccine against Covid-19, coinciding with the time for the inoculation of vaccines against other respiratory viruses (such as flu).
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 acknowledging that the pandemic is approaching a tipping point, the commission concluded 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 will therefore be long-lived . In the long term, public health action is critical, 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 discovered three years ago in China, has spread rapidly around the world and has taken on several variants and subvariants, some of which that are more contagious than others.
In Portugal, vaccination against covid-19 started on December 27, 2020 and since then primary doses and booster doses have been administered in phases.
Source: DN
