HomeBreakthrough COVID Infections Do Not Mean Vaccines Fail

Breakthrough COVID Infections Do Not Mean Vaccines Fail

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Countless news stories and viral social media posts warn of “breakthrough infections” in COVID-19 vaccine recipients. These reports give the false impression that vaccines are ineffective, which can fuel reluctance among millions of Americans who have yet to get vaccinated.

But such infections are not exclusive to COVID vaccination. They frequently occur after influenza, measles, and other vaccinations.

But SARS-CoV-2, the virus that causes COVID, has taught the public more about immunology than any other pathogen, and terms like “breakthrough infections” and “herd immunity” have become widely known.

“It almost feels not just like a microscope but an electron microscope on every single thing that happens with the COVID vaccines,” says Kawsar Talaat, an associate professor in the Johns Hopkins Bloomberg School of Public Health’s department of international health.

And “although some are better than others, most of them have some breakthrough infections,” she says.

A “breakthrough” simply means that a vaccinee tested positive for the disease-causing agent, not that they will become ill or spread the infection. The majority of vaccinated individuals who become infected do not exhibit symptoms, and those who do exhibit mild illness. Even when the SARS-CoV-2 Delta variant is there, the vaccines provide adequate protection against symptomatic disease and death.

On a national level, as of August 9, in the United States, according to the Centers for Disease Control and Prevention, more than 166.5 million people, or just under half of the total population, have received all recommended vaccines. Despite this, 97 percent of those hospitalised with COVID-19 are unvaccinated.

The statistics demonstrate how reality can occasionally become distorted in the public consciousness.

“Anecdotally, from talking to my friends and family and on social media, I think people are more concerned about these breakthrough infections than their prevalence would lead you to be,” Tara Smith, an epidemiology professor at Kent State University’s College of Public Health, agrees.

Another concern with breakthrough cases is the spread of the virus. However, infected individuals “tend to be less likely to transmit, no matter what we’re looking at,” Smith says.

COVID vaccines are made to reduce transmission among those with an asymptomatic breakthrough infection, according to Nick Grassly, a professor in Imperial College London’s department of infectious disease epidemiology.

“So you already have the fact that you’re immunized and less likely to become infected, and even if you are infected, your risk of transmitting the virus is reduced,” he adds.

One reason is that the coronavirus’s quantity, or viral load, is lower in these infections, implying that there is less of it to transmit. It is unknown how this pattern appears with the Delta variant. A study published in late July by the Centers for Disease Control and Prevention found that vaccinated and unvaccinated people had similar viral counts. However, the researchers in that study did not conduct tests to confirm true viral loads or report data on transmission from vaccinated people, and the “unvaccinated” group included individuals who had received only a partial vaccination.

Breakthrough infections do not occur as the covid vaccines are ineffective. Immunity can wane over time, making a vaccine less effective against a specific pathogen. One example is the measles-mumps-rubella (MMR) vaccine, which provides strong protection against measles but less so against mumps, according to Talaat.

Even the powerful measles vaccine has a history of infection outbreaks. Following a measles outbreak in the late 1980s that primarily affected unvaccinated young people, policy was changed to require two doses instead of one. According to Talaat, the first MMR dose provides about 90% lifetime protection, but the second dose covers about half of the remaining 10%. Because of the high contagiousness of measles, getting the most coverage possible is critical.

Influenza vaccines are the inoculations most closely linked to outbreak infections. Because “we know the flu vaccine is not as effective,” Smith says, “there would be so many more” of the former if such cases of flu were tracked as closely as breakthrough SARS-CoV-2 infections. Breakthrough COVID cases, she says, are “just another Wednesday” compared to those that occur with other vaccines.

COVID vaccines appear to be performing better than influenza vaccines. So far, the shots have been effective in neutralising COVID variants. COVID, according to Grassly, does not overcome immunity as well as influenza viruses do. And some strains of influenza are simply better at avoiding whatever human ingenuity throws at them, resulting in flu seasons marked by low vaccine efficacy and a high number of breakthrough cases.

“We’re not calling it ‘breakthrough’ but saying, ‘It’s 47 percent effective this year’ or ‘60 percent….’ We talk about efficacy,” says Talaat.

But even though influenza vaccines have relatively poor efficacy, she says, they are “better than nothing,” saving lives and preventing hospitalizations.

If the vaccinated population is small and the community has a high case count, outbreak rates can rise. High vaccine uptake, on the other hand, means that the vaccinated population accounts for a larger proportion of overall cases. Because almost everyone is immunized, any cases that do occur are more likely to be in someone who has been vaccinated. That was the case in a Massachusetts outbreak, where 74 percent of people who tested positive were vaccinated in a region where only 69 percent of eligible residents were vaccinated.

Other factors, such as age and health conditions associated with a weakened immune system, contribute to an overrepresentation of vaccinated patients with breakthrough infections. Because these patients’ level of immunity often results in a blunted response to the vaccine, they may be at a higher risk than younger, unaffected people who have not been immunized.

Booster shots for COVID, similar to those given for pertussis, may be required in people who have a suppressed immune system or whose immunity is waning. Talaat cites reports of positive responses to a third COVID vaccine dose in organ transplant recipients. For some immunocompromised patients, France and Israel have already added a recommended third dose, while the United Kingdom has yet to do so, and is thinking about it. The Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention met on July 22 to review data on booster shots in immunocompromised people and concluded that a third dose may be necessary for this patient population.

During an earnings call in late July, Pfizer cited unpublished preliminary results for 23 clinical trial participants who showed increased protection against the Delta variant after a third dose of its mRNA vaccine. The company said it expected to submit its third dose findings to the FDA in August in order to obtain emergency use authorization for a booster, according to prepared remarks during the earnings call.

Meanwhile, “we don’t know if boosters will work, but if we vaccinate everybody, then that will protect the 2.7 percent of people in this country who are immunocompromised,” Talaat says.

“And they won’t have to worry about how well or how badly their immune system works to protect against the virus.”

Image by Eva Marie Uzcategui/Bloomberg via Getty Images

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