What we know at this stage about natural immunity to COVID-19

While much of the recent discussion about COVID-19 has focused on those who have been vaccinated versus those who have not been vaccinated, less has been said about those who have gained natural immunity through infection with the virus.

It appears that a previous infection with SARS-CoV-2, the virus that causes COVID-19, offers some immunity to reinfection, although there is an ongoing debate over how much and how long.

Natural immunity “offers pretty good protection, there’s no question about it,” said Dr Liam Sullivan, Grand Rapids infectious disease specialist at Spectrum Health. “The question is how long does this protection last, and I think it’s too early to tell.”

Still, medical experts are strongly encouraging people who have had COVID-19 to get vaccinated, saying there is little downside and growing evidence that it protects against recurring episodes of the virus.

Below is an overview of the latest research on the natural immunity virus.

An estimated 28% of Michigan residents have COVID-19 antibodies that indicate a previous infection.

This is based on the results of 1,352 antigen tests performed in Michigan during the last two weeks of July, according to the federal Centers for Disease Control.

The July estimate that 28.1% of Michigan’s population has antibodies is up from 18.9% at the end of February 2021, just before Michigan’s spring surge.

Based on antigen results from July 2021, the CDC estimates that 34% of Michigan residents under the age of 18 have been infected with the virus so far; 31% of 18 to 49 year olds; 24% of those aged 50 to 64 and 17% of those 65 and over.

The latest data means that around 2.8 million Michiganders have contracted the virus so far, about three times the number of confirmed cases.

The natural infection appears to be strong against the Delta variant.

A new study of Israel suggests that natural immunity may be more protective against the Delta variant than two doses of the Pfizer vaccine. The study compared 16,125 Israelis who were vaccinated in January or February to 16,125 infected with SARS-CoV-2 during that time, and looked at the number of breakthrough cases and re-infections from June 1 to August 14.

The study found 238 breakthrough cases, or 1.5% of the vaccinated group. During this time, among the unvaccinated people, there were 19 re-infections or 0.12% of the group.

The Israeli study also looked at unvaccinated people infected in 2020 and found a higher rate of reinfection than those infected more recently, but the rate of reinfection was still lower than the rate of breakthrough cases for those vaccinated.

Earlier this summer, the Cleveland Clinic published a study of its employees, which found no reinfection among unvaccinated workers who were previously infected with SARS-CoV-2. This study concluded that a previous infection appeared to offer protection similar to vaccination.

But this immunity can vary greatly depending on the strain.

While the Israeli study indicates that infection with the original strain appears to protect against Delta, which originated in India, there have been more re-infections associated with strains originating in South Africa and Brazil.

In the P.1 strain from Brazil, a study found six times lower antibody efficacy against P.1 compared to the original strains of SARS-CoV-2. This study estimated that 25% to 61% of previously infected patients were susceptible to P.1 infection.

Similar problems were found with the South African variant, also known as B.1.351. A vaccine trial for Novavax found that participants in the control group who were previously infected were just as likely to become ill with B.1.351 as those without natural antibodies, suggesting that older strains of COVID-19 failed to provide immunity against B.1.351. In comparison, the vaccine offered some protection.

Vaccines appear to be more consistent in treating mutant strains.

There are important differences in the immunity acquired via an mRNA vaccine compared to natural immunity which suggests that the vaccines may provide more consistent protection against the various COVID-19 mutations, according to a study published in June by the National Institute of Health.

The study focused specifically on the receptor binding domain (RBD), a key region of the spike protein on the outer surface of SARS-CoV-2. He found that “the antibodies generated by the mRNA vaccine were more concentrated on RBD compared to antibodies caused by infection, which more often targeted other parts of the spike protein. It is important to note that the antibodies caused by the vaccine targeted a wider range of locations on the RBD than those caused by natural infection, ”said the NIH.

“These results suggest that the natural immunity and the immunity generated by the SARS-CoV-2 vaccine will differ in the way they recognize new viral variants. In addition, antibodies acquired using a vaccine may be more likely to potently target new variants of SARS-CoV-2, even when the variants carry new mutations in RBD, ”NIH said.

Reinfections are more common in people 65 years of age and older.

Although re-infections are rare, they are more common in older people, according to a Danish study released in March 2021.

The study looked at 4 million Danes infected with the virus to calculate reinfection rates. According to one study, older people seemed to have around 47% protection against repeat infections, compared to younger people who seemed to have around 80% protection against re-infection.

And one study at a Kentucky nursing home found that re-infections in older people tend to be more severe than the first episode of the disease.

This has been his experience, said Dr Michael Zaroukian, a family doctor in the Lansing area who specializes in immunology.

“When people get sick a second time, we see them in the hospital, not just in the office,” he said.

The strength of natural immunity can vary from individual to individual.

Prior exposure to SARS-CoV-2 does not guarantee a high level of antibodies, nor a robust antibody response to the first dose of vaccine, according to a new study from Northwestern University in Chicago.

This study found that people with mild or asymptomatic cases of COVID-19 had a weaker antibody response than those with more severe symptoms.

“Many people and physicians assume that any previous exposure to SARS-CoV-2 will confer immunity to reinfection. Based on this logic, some people who have already been exposed do not think they need to be vaccinated. Or if they get vaccinated, they think they only need the first dose of the two-dose Pfizer / Moderna vaccines, ”said Thomas McCade, a biological anthropologist who was part of the team that conducted the vaccine. the study, in a press release. Press release accompanying the publication of the study.

“Our study shows that prior exposure to SARS-CoV-2 does not guarantee a high level of antibodies, nor a robust antibody response to the first dose of vaccine. For people who have had mild or asymptomatic infections, their antibody response to vaccination is essentially the same as for people who have not been previously exposed. “

Vaccination provides additional protection for people with natural immunity

Unvaccinated people previously infected with SARS-CoV-2 were more than twice as likely to be re-infected as previously infected people who were inoculated, according to a recent study outside of Kentucky.

A similar result was reported in the Israeli study, which also compared previously infected unvaccinated individuals with those who were previously infected and obtained the vaccine. “The latter group had a significantly reduced risk of reinfection,” according to the study.

Colorado fitness trainer Bill Phillips has been a strong advocate for post-infection vaccination after spending two months in hospital during his second battle with COVID-19.

Phillips, 56, decided not to get the shot, believing he was in excellent physical condition and had antibodies that indicated a previous infection. But he caught COVID-19 again in June, ended up on a ventilator and almost died. He recently left the hospital and is in rehab, and a wheelchair and extra oxygen.

“It didn’t help that I could push down on a 300-pound bench or run a mile straight up a hill,” Phillips said. KUSA-TV in Denver. “I made a mistake. This mistake almost cost me my life.

Doctors warn of attempting to deliberately acquire natural immunity

Even though natural immunity may at least offer protection against reinfection of SARS-CoV-2, doctors say it’s a very bad idea for people to deliberately expose themselves to the virus.

“It’s like Russian roulette. You don’t want to roll the dice, ”said Dr Mark Hamed, medical director of the Huron, Lapeer, Sanilac, Tuscola, Alcona, Iosco, Ogemaw and Oscoda County Health Department.

Since the start of the pandemic, nearly 2% of Americans with confirmed COVID-19 have died, 7% have been hospitalized, and 10-30% suffer from “long-term COVID”, which are persistent symptoms such as extreme fatigue, breathing problems, headaches. , brain fog, and organ damage that lasts for weeks or months beyond the initial infection.

The ‘Russian roulette’ factor is also true with children, although younger ones are much less likely to have a severe case of COVID, said Dr Rosemary Olivero, pediatric infectious disease specialist at Spectrum Health in Grand Rapids.

“We are not yet sure whether the natural immunity or the immunity generated by the vaccine is superior in the long term,” she said. “These studies are ongoing and we’re looking for this data all the time, so I can’t really give you a perfect estimate.

“However, because the side effects of a vaccine are extremely low, and the risk of having a negative consequence from COVID-19 probably ranges from 3% to 10% for a child, I think vaccination is the way to go. safer to immunize a population against the virus, ”she said.

After the publication of the Israeli study indicating that natural immunity offers strong protection against reinfection of the Delta virus, the scientists said they did not want to send the wrong message to the public.

“What we don’t want people to say is, ‘Okay, I should go out and get infected, I should throw an infection party,'” said Michel Nussenzweig, immunologist at Rockefeller University. from New York. Scientific journal. “Because someone might die.”

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