Study finds transmission of covid offers ‘very strong’ protection against serious disease if we are re-infected, ‘regardless of the variant’
A first infection also prevents reinfection in 85% of cases, as long as it is anterior variants to ómicron
Against omicron, protection against reinfection drops to 38%, but it remains almost total to avoid severe covid, for 14 months
Much is said about the duration of immunity offered by vaccines. Much less than how long it lasts protection offered by natural infection. How does it protect us from re-infection? And above all, how does it protect us from serious reinfections?
have seen this that the protection against contagion diminishes over time, but also that it prevents the development of serious symptoms if we become re-infected, and that, in turn, shows no signs of diminishing Over the month. For it, says the magazine Nature when the studio resounds“even if the world continues to be hit by waves of covid, they will not overwhelm hospitals”.
It is important to note that, when talking about reinfection, in the study they refer to a second infection with one of the pre-ómicron variants. Although also then studied what happens when reinfection is done with omicron.
Maximum protection seven months after infection
The aim was to investigate how naturally acquired immunity evolves, infecting us. To do this, the authors analyzed the Covid cases recorded in Qatar between February 28, 2020 and June 5, 2022. That is, during more than two years. “Our study is the first to follow this long,” he says. Nature one of the researchers, Hiam Chemaitelly, an epidemiologist at Weill Cornell Medicine in Qatar.
They compared covid cases in people who have not been vaccinated but who have been infected before, with those who have not been vaccinated or who have previously been in contact with the virus. And what did they see?
What having been infected before prevented reinfection in 85.5% of cases. For how long? From 4 months after being infected to 16. Of course infection and re-infection have been with variants prior to ómicron.
Between the 4th and 16th month after the first covidtherefore, they saw that people were quite well protected, that they had little risk of being reinfected. During this period, when was the maximum protection reached?
According to the study, that the natural immunity reached a maximum level of protection, 90.5%, during the seventh month after the first infection. And it fell to 70% at 16 months. The researchers extrapolate this trend and estimate that the effectiveness of natural immunity against reinfection it will fall to 50% at the 22nd month and to less than 10% when 32 months have passed since the first infection. At 36 months, three years after passing covid for the first time, there will be nothing left of this protection.
Less protection if reinfection is done with omicron
What happens when you analyze data from reinfections with omicron? That they confirm a significant drop in the protection generated during this first infection. It was only effective in 38% of recorded reinfections in the first 6 months after the appearance of omicron. And it went down very quickly.
However, there is one important fact. The protection provided by infection with any variant of SARS-CoV-2 is very effective in the fight against serious covid in the event of re-infecting us, whatever the variant.
Almost total protection against serious reinfections
In this study, they found that efficacy was around 100% up to 14 months after the first infection. And it showed no signs of slowing down. “The effectiveness of primary infection against reinfection with severe or fatal covid was 97.3%, regardless of variant of primary infection or reinfection, and with no evidence of decrease“, we read in the study.
The authors also took one thing into account: the majority of Qatar’s population is young, so all of these findings may not apply to older populations. They then analyzed the cases of covid in people over 50 and saw that the levels of protection were “similar”. Natural protection was powerfulnot so much against reinfection as against the severity of this reinfection.
Keep in mind that This is a very large study with a very long follow-up. The study is “solid”, ensures in Nature Shane Crotty, prestigious immunologist from the La Jolla Institute of Immunology in California.
These are data which indicate that the immunity acquired naturally, during a first infection, is very resistant. Or at least it was, before the arrival of the omicrons, its variants and sub-variants to change the situation. But they change it in terms of contagion, of the possibility of reinfecting us. What does not seem to change is the protection that this first infection offers us against severe covid. The researchers themselves warn of this in the conclusions of the study.
“The protection of natural infection against reinfection fades and may decline within a few years. Viral immune evasion accelerates this decline. Protection against severe reinfection remains very strong, with no evidence of decline, regardless of variant, for more than 14 months after primary infection.”