Ómicron: is “natural immunity” better than vaccination? | Science and Ecology | D.W.

Most governments, with the exception of a few like Australia, as demonstrated this week by the drama generated by tennis star Novak Djokovic’s entry into the country, accept “recovered” status as a form of immunity to covid-19. 19. This means that if someone was recently infected and recovered, they are considered adequately immunized.

But how much do antibodies protect against infection compared to those from vaccines? And how is the omicron variant factored into the equation?

The answer to the question is not simple. So far, research suggests it mainly depends on which variant a person was infected with and when they tested positive.

recovery vs. vaccination: what the research says so far

Before the omicron wave, the general scientific rule was that an outbreak of infection (of any variant) provided immunity comparable to a single dose of vaccine, according to Julian Schulze zur Wiesch, head of the department of infectious diseases at the University Medical Center of Hamburg-Eppendorf.

Before omicron became part of the picture, research generally showed that people who had acquired immunity through a Covid-19 infection were protected in the months after infection, but that immunity began to wane after four to six months.

But it is not yet clear whether such preomicron “natural immunity” was more protective than vaccination.

A study published in late October 2021 by the US Centers for Disease Control and Prevention (CDC) found that unvaccinated adults who tested positive three to six months earlier were five times more likely to test positive. than vaccinated adults who had not previously been infected.

This study acknowledged that the research was only conducted in patients with disease severe enough to require hospitalization and that the results cannot be generalized to include outpatients.

Some research suggests that older people are less likely to be protected from re-infection by a previous infection with covid-19.

The CDC report came on the heels of an Israeli study in August with very different results, which found that people who had received the BioNTech/Pfizer vaccine and had not previously tested positive were 13 times more likely to be infected with the virus. the delta variant than people who had been infected but not vaccinated. The research, which has not yet been peer-reviewed, currently qualifies as the largest study comparing immunity gained from prior infection to vaccine-induced immunity. While the CDC study surveyed some 7,000 hospital patients, the Israeli study surveyed more than 30,000 members of the national health system.

“It’s a bit confusing, because there are so many variables,” Zur Wiesch tells DW. This is because our immune response is complex and influenced by many factors: the time of infection, the variant, the type of vaccine we receive, whether we receive boosters, and the overall strength of our immune system.

Age is probably important

Research shows that age is also likely to play a role in whether we will be re-infected after having the virus.

A study involving US war veterans and still undergoing peer review shows that mRNA vaccines offered stronger protection against infection, hospitalization and death among older people than earlier infections of covid-19.

But for participants younger than 65, the protection offered by the vaccines was about the same as that from a previous infection, according to the study. The authors also disclosed that they had received prior financial support from Pfizer.

The study, published in September, supports the findings of another population-level research in Denmark and published in March, which was based on data collected during the second wave of the pandemic in late 2020, before vaccines were widely available. . Among younger people who tested positive during the first wave, protection against a new infection was around 80%. However, among people aged 65 and older, immunity acquired through previous infection was only about 47%.

And how does omicron influence immunity?

The omicron wave is so new that no conclusive data is yet available on the quality of immunity provided through infection, but it is likely to be similar to other variants, Zur Wiesch says. That means that if someone has been infected with omicron in the past few weeks, they are probably safe from reinfection for months to come.

But because omicron has a higher rate of transmissibility than previous strains, higher levels of antibodies are needed to prevent infection. Immunity gained through just two vaccinations or infection with earlier variants of covid-19 (such as delta or alpha) will not necessarily prevent omicron infection, Zur Wiesch says. Also, regardless of whether a person was previously infected or vaccinated twice, a booster is the best defense against re-infection.

A booster shot is the best defense against covid-10 infections, experts say

A booster shot is the best defense against covid-10 infections, experts say

The efficacy of protection against omicron provided by “natural immunity” from other coronavirus variants may be as low as 19%, according to a study conducted by Imperial College London’s COVID-19 response team in late December 2021 .

Thus, early findings generally indicate that as long as you have some form of immunity, either through two doses of a vaccine or a previous infection plus a single dose, an omicron infection is likely to be mild.

Does “super immunity” exist?

The body seems to respond best to a cocktail of mixed immunity, according to Zur Wiesch, citing a study his team conducted among German health workers in 2021. Patients who received different types of vaccines, the one from AstraZeneca, for example, and then a dose of Moderna and a booster, seemed to have some of the best protection.

Other studies have indicated that people with a combination of immunity acquired through a past infection plus two injections seem to have the best results. Immunologists have called this phenomenon “hybrid” immunity or “super” immunity.

Also, while some research shows that the severity of infection might increase antibodies, other studies have found no difference.

But these findings don’t take omicron into account, so we don’t yet know if they translate to the current wave, Zur Wiesch says, adding that for now we’ll just have to wait for the science.

Despite the unknowns, one thing is clear to Zur Wiesch: Unless a person has been infected with omicron in the last week or two, a vaccine or booster is their best chance of avoiding contracting COVID-19 and passing it on to others. others.

(rr/mn)

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