The many people who have survived a SARS-CoV-2 infection in the recent past – even despite vaccinations – can feel safe for some time. Surviving Covid-19 disease protects up to 90 percent from a serious or fatal illness for at least ten months. This has resulted in a large meta-analysis by US experts.
The evaluation of 65 scientific studies from 19 countries on the subject of immunity against renewed infection or symptomatic and serious diseases after a SARS-CoV-2 infection included all virus variants that have appeared internationally (Wuhan, Alpha, Beta, Delta and Omicron BA.1) until September 31, 2022. The publication by experts around Stephen Lim from the University of Washington (Seattle/USA) took place a few days ago in the medical journal “Lancet” (Online; DOI: 10.1016/S0140-6736(22) 02465-5).
Overall, there was a fairly uniform picture as far as the protective effect against a new infection was concerned. “The effectiveness against re-infection by the Omikron BA.1 variant (after initial infection; note) was 45.3 percent and against symptomatic Omikron BA.1 disease 44 percent,” the experts wrote. A first infection of any SARS-CoV-2 type caused more than 78 percent protection against serious or fatal diseases against all virus variants, including against Omicron BA.1.
The time course is also interesting. In the case of an infection with a pre-omega variant, the protection rate against re-infection with the wild type (Wuhan) and against the variants alpha and delta was 85.2 percent after one month, 78.6 percent after 40 weeks, and 78.6 percent after 20 weeks months still at 55.5 percent.
Protection from re-infection decreased more rapidly
In contrast, the protection against re-infection with Omikron BA.1 decreased much faster and was only 36.1 percent after ten months. The protection against symptomatic disease achieved by infection with a pre-omega variant corresponded to the estimates for reinfection, as the German Medical Journal also stated on the study: it protected against symptomatic disease caused by the wild type and the alpha and delta variants 78.4 percent after ten months. In contrast, they only prevented 37.7 percent of a symptomatic disease caused by Omicron BA.1.
However, the protective effect against serious and fatal diseases caused by the Covid-19 pathogen seems particularly important. After ten months, an initial infection with the Omicron virus variants (Wuhan, Alpha, Delta) protected 90.2 percent from a serious or even fatal further illness.
After 40 weeks, an Omicron BA.1 infection still showed a protection rate of 88.9 percent against another infection with a severe to fatal course. “The protection rate from the BA.1 variant was significantly lower and also decreased more quickly,” the US scientists summarized their results. The safest way to get effective immunity against SARS-CoV-2 – especially protection against severe disease progression – is still vaccination.
