Breakthrough infections and booster shots: what you need to know | Vaccines and vaccination

Federal health officials have recommended booster shots for all adults fully vaccinated against Covid-19 with the Pfizer or Moderna vaccines, citing evidence suggesting that breakthrough infections may become more common over time.

The plan has come under scrutiny. Some American scientists said there was insufficient data to support the decision and that vaccines remain highly effective against serious illnesses requiring hospitalization and death. The World Health Organization has severely criticized U.S. leaders for using vaccines to provide people with a third injection, even though most people around the world have not had one.

Health officials also said it was possible that people who received the Johnson & Johnson single-dose vaccine would need a booster, but said they were waiting for more data.

Here’s what you need to know about the latest booster shots and breakthrough infections:

What did we learn about breakthrough infections this week?

First, it’s important to note that the current devastating wave of Covid-19 in the United States is an “unvaccinated pandemic,” with the overwhelming majority of hospitalizations among unvaccinated patients. Deaths of vaccinated individuals remain extremely rare.

Federal authorities have said new data suggests that mild to moderate breakthrough infections in people who have received messenger RNA vaccines (Moderna and Pfizer Covid-19 injections) may become more frequent as people have received. their vaccines.

It is a “waning” immunity that prompted their decision this week to offer booster shots to people who received their second Pfizer or Moderna injection eight months ago.

When administration officials made the announcement, the CDC released three reports, which officials say supported their decision. These studies provided real-world insight into how vaccines protect against infection and hospitalization.

The first was a large study of nursing home residents, who tend to be frail and elderly. The study found the vaccine to be effective against infection declined, coinciding with when the Delta variant became more dominant.

Before Delta, mRNA vaccines provided 74.7% protection against infection for this demographic. After Delta, these vaccines provided protection against infection 53.1% of the time. The study only tells us about the infection, not the severity of the disease, as the study authors only documented infected patients compared to patients without Covid.

In a second study, researchers crossed databases with hospitalizations and vaccination status in New York City. The study found the vaccine to be effective against infection rose from 91.7% to 79.8% by the time Delta became dominant. However, they also found the vaccine to be effective against a serious disease requiring hospitalization has remained “relatively stable”.

“The Covid-19 vaccines have been very effective against hospitalization,” over 90%, “for fully vaccinated New Yorkers.” This was true for the Delta variant.

A third multi-state study examined more than 1,100 patients and found that there was “no decline in vaccine effectiveness against hospitalization of Covid-19” over a 24-week period. However, he found that the vaccine’s effectiveness was lower in people with weakened immune systems.

What do these studies tell us?

Taken together, these studies appear to show the vaccine’s effectiveness against infection decreases, which scientists expected; but protection against serious illnesses requiring hospitalization remains high.

This explains why a separate analysis has shown that the vast majority of patients hospitalized in the current fourth wave – over 94% – are not vaccinated and that deaths among fully vaccinated individuals are “effectively zero”. Currently, 51% of all Americans are fully immunized, although coverage varies widely by location.

Despite the high degree of protection against hospitalization that these studies revealed, the Biden administration said immunity “could” decline in the future, even with severe results, and stressed that the boosters would help Americans. to “stay ahead of this virus”.

“Even though this new data affirms that vaccine protection remains high against the worst consequences of Covid, we are concerned that this pattern of decline that we are seeing will continue in the months to come,” said US Surgeon General Dr Vivek Murthy . This pattern of declining immunity “could lead to reduced protection against serious illness, hospitalization and death.”

In case it is helpful or illustrative, I have modified a graph to explain the rationale for the third “booster” mRNA immunization. pic.twitter.com/rk4InUnt4D

– Prof Peter Hotez MD PhD (@PeterHotez) August 18, 2021

However, while many scientists predicted that boosters would be needed, some wondered if the data now supports their distribution. For example, the evidence presented by the administration did not show whether a pattern of declining immunity for mild and moderate disease will result in decreased immunity against hospitalization and death.

“They seem to imply, at least to me, that the tendency for the vaccine to decrease in effectiveness for mild to moderate disease could extend to moderate to severe disease,” said Dr. William Moss, professor at the Johns Hopkins University Bloomberg School of Public Health and Executive Director. of the International Vaccine Access Center. “It’s a hypothesis they’re making, we don’t have proof.”

White House Chief Medical Advisor Dr Anthony Fauci also presented evidence that antibody levels rise dramatically after a booster. That would be to be expected. However, how long this increased immunity could last is unknown.

This has raised concerns that increased protection against mild to moderate illness is only temporary and may not be worth the effort and supplies when billions of people around the world lack access. vaccines.

As Anna Durbin, a vaccine researcher at Johns Hopkins University, told Stat News, “We can’t keep [boosting] and say, “We’re going to avoid colds in everyone.” “

What does it mean to keep me safe?

First of all, if you haven’t already, get vaccinated. It is the best way to protect yourself and the people around you from infection, hospitalization and death from Covid-19.

The vaccines have been reviewed by several independent scientific panels, and before the boosters are rolled out in the United States in September, the vaccines from Pfizer and Moderna will again be reviewed by the Food and Drug Administration and a CDC advisory panel. While there has been a debate among scientists as to whether boosters are really necessary for all Americans, no safety concerns have been raised.

If you are fully vaccinated, your own risk level for a breakthrough infection will depend on your particular situation. People with moderately to severely weakened immune systems are already eligible for a third injection of the mRNA vaccine. The elderly may also be at an increased risk of acute infection and may have more serious illness.

The good news is that old-fashioned public health measures (the ones everyone is familiar with now) still work. Masking, social distancing and hand washing can significantly reduce potential exposure to the virus, along with the high degree of protection offered by the vaccine. Children under 12, who are not yet eligible for the vaccine, should practice masking in schools, according to the CDC.

People who live in areas of high transmission, which at this stage are most of the United States, are also more likely to be regularly exposed to the virus, which could lead to a breakthrough infection. Masking and social distancing in public is most important in these areas.

As more people are vaccinated, breakthrough infections will represent a higher proportion of overall infections. This is not a sign that the vaccines are failing.

What does this mean for the future of the pandemic?

“Our number one, two and three priority is to vaccinate the unvaccinated,” Moss said. Booster shots will not significantly reduce the spread of Covid-19 – but getting new people vaccinated will.

This means that vaccinating people with initial doses in the United States and around the world is important, because wherever Covid-19 spreads widely, the virus can develop new variants and escape the protection provided by vaccines.

Even though the United States has pledged to donate more than 600 million doses of vaccine worldwide, it is a “drop in the bucket” of the billions needed. This leaves the world vulnerable to new variations.

The virus will be with us – probably for the rest of our lives. Indeed, many people will be exposed to Covid in their lifetime, perhaps several times.

“We are not going to eliminate, eradicate this virus,” Moss said. The long-term goal at the population level is to prevent serious disease, Moss said, and the safest way to do that is through vaccination.