Naturally acquired immunity against Covid-19 infection lasts longer than vaccine-acquired immunity and is nearly 100-percent effective against severe infection, a new study from Qatar finds.
“While current coronavirus disease 2019 (COVID-19) vaccines had a critical role in reducing COVID-19 hospitalizations and deaths, their rapidly waning immune protection, particularly against the Omicron … variant, limits their role in shaping the future of SARS-CoV-2 epidemiology compared to other vaccines,” reads the study, a preprint version of which was posted on medRxiv.
That being the case, the researchers decided to investigate the role natural immunity is likely to play in restraining Covid-19 in the coming years. They sought to answer the following questions: “1) When infected with a pre-Omicron variant, how long does protection persist against reinfection with pre-Omicron variants? 2) When infected with a pre-Omicron variant, how long does protection persist against reinfection with an Omicron subvariant? 3) When infected with any variant, how long does protection persist against severe, critical, or fatal COVID-19?”
They reviewed the relevant data on Covid-19 infections in the entire population of Qatar (about 2.9 million people), comparing the outcomes of individuals who had previously been infected with Covid-19 to the outcomes of those who had been neither infected nor vaccinated (the “infection-naïve”). While the population of Qatar is “internationally diverse,” they pointed out, it is also “predominately young and male.” However, based on analysis of the data they gathered on individuals aged 50 and older, they believe their findings also apply to countries with older populations.
Individuals who had been infected with a pre-Omicron variant of the coronavirus were considerably less likely (1.7 percent) than those who were infection-naïve (9.6 percent) to become reinfected with a pre-Omicron variant. Overall, pre-Omicron infection was 85.5-percent effective against pre-Omicron reinfection, though it slowly waned over time. “Effectiveness of pre-Omicron primary infection against severe, critical, or fatal COVID-19 due to pre-Omicron reinfection,” the researchers found, “was 98.0%.”
Pre-Omicron infection was considerably less effective in preventing reinfection with one of the highly contagious Omicron subvariants. Nearly seven percent of previously infected individuals contracted an Omicron subvariant, while over 10 percent of infection-naïve individuals came down with one. Pre-Omicron infection, in fact, was just 38.1-percent effective against Omicron infection. Nevertheless, it was still 88.6-percent effective in keeping the infection from becoming severe.
Prior infection with any variant, pre- or post-Omicron, was astoundingly effective at keeping future infections of any variant from threatening their hosts. For the first 14 months after the initial infection, effectiveness at preventing severe infection was approximately 100 percent, after which it slowly dropped to a still-impressive 97.3 percent. “Effectiveness of primary infection with any variant against reinfection with any variant was 69.4%,” the authors wrote.
While the study found that the protection against reinfection provided by natural immunity falls over time, “this waning in natural immunity mirrors that of vaccine immunity, but at a slower rate,” they noted. “Vaccine immunity may last for only a year, but natural immunity … may last for 3 years.” When it comes to Omicron subvariants, natural immunity may last more than twice as long as vaccine immunity.
“Despite waning protection against reinfection, strikingly, there was no evidence for waning of protection against severe COVID-19 at reinfection,” the researchers observed. This, too, is similar to vaccine immunity — but, of course, without any of the harmful side effects.
The authors suggest that Covid-19 “may exhibit a similar pattern” to the common cold, which is also caused by coronaviruses. Colds can induce short-term reinfection protection but “life-long immunity against severe reinfection,” so even if “viral evolution and immune invasion” cause “periodic (possibly annual) waves of infection” with Covid-19 variants, “the lasting immunity against severe reinfection will contribute to a pattern of benign infection. Most primary infections would occur in childhood and would likely not be severe. Adults would only experience periodic reinfections, also not likely to be severe.”
In other words, as the non-alarmists have long argued, letting the virus work its way through the population is the only long-term solution to its dangers — dangers that have already significantly diminished and will continue to wane over time. But try telling that to the mask-and-vax crowd that still holds sway in so many cities and countries.
