Yes, we probably need coronavirus booster shots – but which one?

WASHINGTON – Scientists in the United States are doing everything they can to determine whether people who have received the complete immunization schedule against Covid-19 they will need booster doses, and if so, if those booster shots can be from another brand.

For those eager to emerge from the health crisis, the relief of being vaccinated is replaced with a new concern: Is immunity a countdown? Can you plan a family wedding for the second half of the year? Will everyone need to get reminders of the vaccine? When? Are we all “attached” to the brand or type of vaccine we received first, and will the booster have to be the same?

“We already know that Covid is not going to go away, and we also know that antibodies decrease over time, so at some point we will need a boost. What I can’t predict is when, ”says John Biegel, assistant director of clinical research in the Division of Microbiology at the National Institute of Allergy and Infectious Diseases (NIAID) in the United States.

Beigel is working on a clinical trial that will answer one of these questions, as it will test whether different doses can be alternated if necessary. A person who has received the first two doses of the Pfizer-BioNTech vaccine at the start of the year, give yourself a third dose of Modern? Is it a benefit or a risk to switch from one brand or vaccine technology to another?

The trials in the United States come as health experts in China are already recommending a third dose for some people at risk. Scientists know that vaccine-induced immunity to most diseases wanes over time, but the specific response in the case of the coronavirus will only come in the weeks and months to come.

To begin with, scientists must first identify a threshold: what is the minimum level of immunity sufficient to protect a person? Then they will need to study the time it usually takes for immunity to drop to that level. And finally, they must find the best way to boost or strengthen that immunity.

By next month, Beigel hopes to have the results of studies of people who have fallen ill after being vaccinated in clinical trials, findings that could help establish a threshold of immunity, which the researchers said. scientists call it a “correlate of protection”. These studies could help researchers establish a minimal level of antibodies that indicate whether a person is immune or whether that person is vulnerable to infection again.

Scientists are analyzing blood samples from the first people vaccinated a year ago, as part of clinical trials of the vaccines, in hopes of determining whether the antibodies persist or have disappeared. Previous research has found that antibodies to the disease remain at solid levels for at least six months after vaccination with Moderna’s formula, although viral variants can complicate the picture and cause antibody protection to wane more quickly. A recent study published in Nature found that the antibodies decrease after the infection has healed, but do not continue to drop: they stabilize and are still present almost a year later.

The clinical trial launched by the NIAID will systematically test whether people who received a brand of vaccine in January (the single Johnson & Johnson dose, or both doses of Moderna or Pfizer-BioNTech vaccine) are required to receive a boost in the same Mark. or if there are advantages to alternating and combining vaccines.

“People need to understand the limitations of the data we process so far and the critical importance of getting data to make future decisions based on confirmed information,” Beigel said. “We assume it’s okay to give a booster dose of any other vaccine, but we want to be sure.”

For people like Martin Silberberg, 76, a retired biochemist and textbook author from the town of Pelham, Massachusetts, these questions have come to the fore. Silberberg and his wife were vaccinated in February and March. They would like to travel to Scotland in September to attend a family wedding, but are concerned both about the possibility that their immunity will have waned by then, and the confusing information circulating about vaccine ‘passports’.

As for shorter trips, they hope to attend museums and chamber music concerts, and be able to go out to eat, even if it’s cold. Silberberg would love to get a booster or even an antibody count test to see if he’s still protected, but he’s still reaching the frontier of the unknown. The Food and Drug Administration (FDA) has advised against antibody testing, primarily because it’s still unclear how to interpret whether or not the result of a particular test indicates a sufficient level of immunity.

“My friends are my age and we all wonder the same, not knowing what to do,” says Silberberg. “After how long should you start to worry?”

Scientists are monitoring various data streams for disturbing clues. They’ll be watching closely what happens to people who get vaccinated in clinical trials and in the real world, in part because lowering antibodies doesn’t necessarily mean people get sick, because the body has other types of immune responses. , what they can. be activated and defend ourselves against infection.

If scientists find a surprisingly high number of infections in those vaccinated, especially infections that cause serious illness, that would be a warning sign that booster doses are needed.

Antibody

A recent study of Moderna’s vaccine found that after six months, antibodies capable of neutralizing the B.1.351 variant fell below the detection level in almost half of those who received the vaccine. But these lab tests can’t predict what would happen if vaccinees were exposed to the variant after that time.

One possibility is that these people get sick, But it can also happen that despite the decrease in antibodies, after infection “the immune system quickly recognizes the virus and continues to protect us”says John Mascola, director of the NIAID Center for Vaccine Research.

Pharmaceuticals are already testing boosters, including an extra dose of their own vaccines, as well as reformulated boosters especially against the variant. A trial with Moderna boosters showed that a third dose and a specific version against the B.1.351 variant increased antibody levels, an encouraging sign. A study of another booster option that would provide protection against the parent strain and the variant-specific virus is also underway.

Testing the alternation and combination of different brands and formulations of vaccines should help answer practical questions about how best to use their immunizing properties. The results of these tests will be ready by July or August, in the hope that the data will help make decisions before next fall and the arrival of cold in the northern hemisphere, says Beigel.

The trial will test which combinations work best and may end up showing that all can be used. This would make logistics a lot easier, as people would not be tied to the availability of a specific brand or formula.

The trial will study groups of 50 people fully vaccinated with a licensed vaccine, and each group will test the combination with another formulation. Monitoring antibody levels after vaccination will show whether the boosters are having the desired effect of boosting immunity and may reveal whether certain combinations are more effective than others.

John P. Moore, an immunologist at the Weill Cornell School of Medicine, says it will be public health officials and scientists, not drug companies, who will decide if and when boosters are needed.

Moore warns that the idea of ​​”lowering immunity” is less terrifying than it sounds. The protective shield that vaccines provide will not suddenly disappear, and although trials have shown that vaccines are slightly less effective against the spread of certain variants, they still provide strong protection against serious illness and death.

Since vaccines have been in use for months, even as immunity wanes, the world will never be suddenly left unprotected at the same time. “Antibody levels never drop,” Moore said. “Either way, it will be a gradual process.”

The Washington Post

Translation of Jaime Arrambide

The Washington Post

Conocé The Trust Project