Is Covid’s “natural immunity” better than a vaccine?

© Marco Bello / Reuters
Although researchers are not sure whether a vaccine or the infection itself produces a stronger immune response, one thing is clear: the vaccine is much safer.

In the wake of last month’s announcement of the astonishing results of Pfizer and Moderna’s experimental Covid-19 vaccines, Senator Rand Paul tweeted a provocative comparison.

The new vaccines were 90% and 94.5% effective, said Mr. Paul, Republican of Kentucky. But “naturally acquired” Covid-19 was even better, at 99.9982 percent efficiency, he said.

Mr Paul is one of many who, weary of lockdowns and economic losses, have touted the benefits of contracting the coronavirus. The senator was diagnosed with the disease this year and has argued that surviving an episode of Covid-19 provides greater protection, and poses less risk, than to get vaccinated.

The problem with this logic is that it’s difficult to predict who will survive infection unscathed, said Jennifer Gommerman, an immunologist at the University of Toronto. With all the unknowns – like a region’s hospitable capacity or the strength of a person’s immune response – choosing disease over vaccine is “a very bad decision,” she said.

The main advantage of a vaccine is that it is predictable and safe, she said. “It has been optimally designed to generate an effective immune response.”

But what do we know about the comparison between immunity against a previous infection and the protection offered by new vaccines? What If You Have Ever Had Covid – Is It Safe To Get Vaccinated? We asked experts to weigh in on the latest evidence.

Who produces a stronger immune response: a natural infection or a vaccine?

The short answer: we don’t know. But the Covid-19 vaccines have prevented the disease, and they’re a much safer bet, experts said.

Vaccines against certain pathogens, such as pneumococcal bacteria, induce better immunity than natural infection. Early evidence suggests that Covid-19 vaccines may fall into this category. Volunteers who received the Moderna vaccine had more antibodies – a marker of the immune response – in their blood than people who had been diagnosed with Covid-19.

In other cases, however, a natural infection is more potent than a vaccine. For example, having mumps – which can cause infertility in men – generates lifelong immunity, but some people who have received one or two doses of the vaccine still get the disease.

About Mr Paul: The natural immunity to the coronavirus is fortunately quite strong. A large majority of those infected produce at least antibodies and immune cells capable of fighting infection. And the evidence so far suggests that this protection will persist for years, preventing serious illness and even reinfection.

But there is a “massive dynamic range” in this immune response, with a 200-fold difference in antibody levels.

In people who are only mildly ill, the immune protection that can prevent a second infection may wane over a few months. “These people may benefit more from the vaccine than others,” said Bill Hanage, epidemiologist at Harvard TH Chan School of Public Health.

The diversity of the immune response to natural infection could be due to differences in the amount of virus to which the person has been exposed.

With a vaccine, everyone gets the same dose. “We know the dose given and we know that dose is effective in triggering an immune response,” said Dr. Gommerman. “So it becomes a variable that is taken off the table when you receive the vaccine.”

I am young, healthy and at low risk of Covid. Why not try my luck with this rather than get vaccinated in a rush?

Experts were unanimous in their response: Covid-19 is by far the most dangerous option.

“Clearly one is less of a problem for the body to recover from than the other – there is a greater risk of natural infection,” said Marion Pepper, immunologist at the University of Washington in Seattle. .

People who are obese or have diseases like diabetes are particularly susceptible to severe cases of Covid-19. On average, the virus seems less risky for young people, and women tend to fare better than men. But beyond these general generalizations, doctors don’t know why some people get very sick and die while others have no symptoms.

For example, people with certain mutations in immune genes are more susceptible to the disease, several studies have shown. “So there is a risk factor that has nothing to do with age,” said Dr Gommerman.

In a study of more than 3,000 people, aged 18 to 34, who were hospitalized for Covid, 20% required intensive care and 3% died.

“It is true that most people will not be hospitalized, most people will not go to the intensive care unit or die,” said Dr. Yvonne Maldonado, who represents the American Academy of Pediatrics. at federal government meetings. Advisory Committee on Immunization Practices.

But “no one is immune to serious illness,” she said. And while people are not at high risk of Covid themselves, their friends or family could be.

Up to one in three people who recover from Covid have chronic complaints, including exhaustion and a pounding heart, for months afterward. This includes people under 35 without a previous health problem. Some Covid survivors are also showing disturbing signs of their body turning on itself, with symptoms similar to those of lupus and rheumatoid arthritis.

Covid vaccines, on the other hand, carry a little-known risk. They have been tested in tens of thousands of people without serious side effects – at least so far. “Once you start immunizing millions of people, you might find some very, very rare events,” Dr Hanage said. “But we have to know that they are very, very rare and much rarer than the adverse events associated with natural infection.”

I had Covid. Is it safe for me to get vaccinated? If so, when can I get one?

It is safe, and possibly even beneficial, for anyone who has had Covid to get vaccinated at some point, experts have said.

“There is nothing deleterious about getting a boost to an immune response that you had before,” said Dr. Pepper. “You could get an even better immune response by boosting the immunity you had from the first infection with a vaccine.”

In fact, in a meeting on Wednesday, Dr Moncef Slaoui, chief advisor to Operation Warp Speed, said that up to 10% of vaccine clinical trial participants had been infected with the virus without knowing it. Their immune responses to the vaccine are being analyzed, he said.

If you’ve had Covid-19 before, you can afford to wait a while for the vaccine.

Studies by Dr Pepper’s team and others have shown that the immune response changes in the first few months after infection, but everyone who has had Covid has some level of protection during this time.

“We haven’t seen anyone who hasn’t developed some sort of immune response,” she says. “I don’t think these people have to rush out and go for the vaccine the same way very sensitive people really do.”

ACIP, which makes recommendations to the Centers for Disease Control and Prevention on vaccine distribution, said in a meeting Wednesday that people who had not been infected should be given priority over those who contracted the virus. in the last 90 days.

“At some point we’ll have to figure out if 90 days is the right number,” Dr. Maldonado said. But for now, “people who have recently shown signs of infection probably shouldn’t be vaccinated early on because there are so few vaccines available.”