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How strong can I get immune protection after contracting the new crown virus?
Written by | Ling Jun
Source | "Medical Community" public account
On April 20, a real-world study published by researchers at the University of Chicago in jama Network Open showed:
Previously symptomatic COVID-19 infections provide protection comparable to the level of mRNA vaccination, and the duration of protection is even longer than that of mRNA vaccination.
The study, which included data on patients who were tested for COVID-19 in 1,300 health facilities in six U.S. states, followed more than 120,000 participants for up to nearly 8 months, making it one of the largest real-world studies of its kind.
The study was conducted from October 1, 2020 to November 21, 2021.
Of the 121615 unvaccinated trial participants, 24,043 were infected with COVID-19 before enrolment, with a median follow-up of about half a year. The results show:
Throughout the study period, 98 of the 24,043 people who were formerly infected with COVID-19 were re-infected. Of the 97,572 people in the control group, 2,762 were infected with the new crown virus.
After adjusting for the age, sex, race, and other factors of the two groups of subjects through the analysis model, the researchers calculated an exact set of protective data:
The protection rate against secondary infection from previous COVID-19 is 85%, while the protection rate against secondary infection is 88% for moderate and severe illness.
This is almost identical to the previously published data on the protective power of the mRNA vaccine, and it is worth mentioning that the researchers found that the immune protection cycle obtained by natural infections seems to be longer. The level of protection has remained stable for nearly 8 months.
A condition in which natural infection provides immune protection over time
For comparison, a large number of previous studies have suggested that 6 months after the whole new crown vaccination, the vaccines of different technical routes have experienced different degrees of protection.
The researchers say such results provide new insights into the length of protection after initial infection in unvaccinated people and could have important implications for vaccination guidelines and public health policies.
Natural immunity that cannot be ignored
This is not the first study to compare covid-19 infection with post-vaccination levels of protection.
Previously, a series of laboratory studies have shown that for different types of COVID-19 mutant strains, vaccinated people produce much higher titers of neutralizing antibodies than people who have not been vaccinated but have been infected with COVID-19.
Based on such data, the conclusion seems to be that vaccination provides much more protection than natural infection. But this doesn't seem to be the case in the real world:
In March 2021, Danish researchers conducted an observational study of about 500,000 residents of the country, and after correcting variables, calculated that COVID-19 infection provided about 80.5% protection against reinfection.
Another retrospective study conducted in Israel in August of the same year found that patients who were infected with COVID-19 at the same time but were not vaccinated had a 13-fold lower risk of subsequent infection with the Delta strain than those who had received a dose of the mRNA vaccine.
Why does lab data contradict real-world conditions? Lu Mengji, a German-American virologist and professor at the Institute of Virology at the University of Essen School of Medicine, told the "medical community" that such real-world results were expected.
"For a number of reasons, such as test conditions and cost, most of the current research conducted by laboratories around the world mainly targets neutralizing antibody titers produced after acquired immunity." "Therefore, there is a cognitive misunderstanding that 'neutralizing antibody titers' is the gold standard for assessing 'COVID-19 protection'," Lu said. ”
"Vaccination with the new crown can activate humoral and cellular immunity to varying degrees, in addition to the body's natural immunity, that is, non-specific immunity, the initial new crown virus infection can activate this system, to provide protection against secondary infection, but there are fewer related studies."
Israeli scholars also mentioned in the above-mentioned August 2020 study that the "new crown protein immunity" response produced by natural immune activation is more extensive than the "anti-spike protein immunity" stimulated by the new crown vaccine.
Lu Mengji further explained, "In layman's terms, vaccines are specific targets for viruses, but their potency gradually decreases as the new coronavirus strains continue to mutate. In contrast, the new crown protein targeted by natural immunity is more 'broad-spectrum' and is relatively less affected by strain variation. ”
This may also be one of the important reasons why many overseas countries experienced a wave of peak epidemics at the beginning of the year, but now they are gradually tending to ease and normalize. Lu Mengji told the "medical community" that some overseas scholars believe that on the basis of the original vaccination, the Omilon infection is equivalent to an immunization boost.
But Lu Mengji also reminded that this conclusion cannot be simply understood as: active infection with the new crown virus is equivalent to strengthening immunity.
"For high-risk groups and unvaccinated people, even with the less toxic Omiljung variant, there are still significant health risks associated with infection. This is also the reason why the early overseas 'herd immunity' strategy was criticized, and there was no effective vaccine at that time, which was a last resort. ”
"The most important thing now is to increase vaccination rates, provide basic immune protection for the population, and minimize the health risks of COVID-19 infection." Lu Mengji said, "On this basis, in the future, it is possible for us to overcome the long-term threat of the new crown by repeatedly contacting the virus and exerting our own immunity." ”
bibliography:
[1] Comparing SARS-CoV-2 natural immunity to vaccine-induced immunity:reinfections versus breakthrough infections，https://www.medrxiv.org/content/10.1101/2021.08.24.21262415v1.full-text
[2] Protective immunity after recovery from SARS-CoV-2 infection，https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(21)00676-9/fulltext
[3] Rates of COVID-19 Among Unvaccinated Adults With Prior COVID-19，https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2791312
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