What are my chances of getting COVID-19 after being vaccinated?

A few "breakthrough" COVID-19 cases in vaccinated folks are being widely reported. We asked experts what this means

By Matthew Rozsa
April 17, 2021 2:00PM (UTC)
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Digital generated image of circular pattern made out of Syringes with COVID-19 vaccine targeting into coronavirus cell (Getty Images)

A new report reveals that 5,800 people who have been fully vaccinated against SARS-CoV-2, the virus which caused COVID-19, have developed infections anyway.

5,800 might sound like a lot of people — and indeed, experts fear that the number reported without context might lead to greater vaccine hesitancy. Yet it is important to note that these numbers, which come courtesy of the Centers for Disease Control and Prevention (CDC), constitute a very small fraction of the total number of vaccinated Americans.

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As of two days ago 125.8 million (38.3%) of the US population has received at least one dose of a COVID-19 vaccine, and 78.5 million (23.9%) have been fully vaccinated. Vaccines for virtually any disease will wind up being ineffective in at least a handful of cases, since even a vaccine that is almost entirely effective will be eventually given to individuals for whom they do not work.

Even so, one of the goals of mass vaccination is to bring life back to what it was like before the pandemic. While it is reassuring that the CDC added in its email to CNN that "to date, no unexpected patterns have been identified in case demographics or vaccine characteristics," the possibility of a vaccine not working is still there, and the public should still be informed about what that means.

Salon reached out to public health and medical experts for answers about how we should react to the news about "breakthrough infections" — the technical term for a situation in which someone becomes sick with a disease that they were vaccinated to prevent. 

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How do the COVID-19 vaccines work? 

First, note that not all of the vaccines operate in the same way. The Pfizer and Moderna vaccines use a new technology. Known as mRNA vaccines, these vaccines contain a piece of the SARS-CoV-2 virus' RNA that is associated with one specific protein on the surface of the virus — not the whole virus. Once injected into the body, one's cells learn to recognize proteins associated with the dangerous pathogen. It currently requires two shots to be inoculated using these mRNA vaccines; Pfizer's CEO recently said a third shot may be necessary).

By contrast, the Johnson & Johnson vaccine — which has been put on "pause" by the FDA due to a rare blood clot issue — is an adenovirus vaccine, a more traditional vaccine platform. That vaccine only requires one shot.

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What are the chances of someone developing a breakthrough infection?

Dr. Monica Gandhi, infectious disease doctor and professor of medicine at the University of California–San Francisco, told Salon by email that the chances of developing a breakthrough case after being fully vaccinated with an mRNA vaccine are "very low." She pointed to the extremely small percentage of Americans who have had breakthrough cases (far, far, far below 1%) and also cited data from the CDC MMWR study that analyzed real-world effectiveness in both health care workers and first-line responders, as well as the Pfizer April 1 press release. (She added that we don't have analogous data yet for the Johnson & Johnson vaccine.)

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"The chances of fully vaccinated individuals getting infected with any variant of SARS-CoV-2 are limited," Dr. Irwin Redlener, leader of Columbia University's Pandemic Response Initiative, told Salon by email. At the same time, he added that no vaccine is "100% effective," which should guide how we perceive the vaccination movement.

"90% protection is excellent — but it also means that if you vaccinate 1 million people, up to 100,000 could have some level of breakthrough infection," Redlener explained. "That said, most of those who do get infected, few will have serious disease and/or not survive. The difference between those who have had a single vs. [two] doses of Moderna's or Pfizer's vaccine is just a matter of level and sustainability of immune response."

In other words, even if you get vaccinated and then later get COVID-19, you're unlikely to have a serious case.

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Is there anything that will make it more likely for someone to get a breakthrough case after they are already vaccinated?

There are a number of "reasonable hypotheses" about this, but it is not yet known, explained Dr. Russell Medford, Chairman of the Center for Global Health Innovation and Global Health Crisis Coordination Center.

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"While the reported CDC data strengthens our confidence in the high efficacy of our current vaccines, more research is needed to determine what specific factor(s), of the individual, the vaccine and the virus, may predispose a given individual to infection to the virus after vaccination," Medford told Salon by email. These could range from the details of the vaccines and the virus strains to a person's age and underlying health conditions.

Dr. Alfred Sommer, dean emeritus and professor of epidemiology at Johns Hopkins University, told Salon that "the risk of infection and especially severe disease is reduced by vaccination, but not eliminated entirely." Sommer clarified that potential risk "increases the greater that person's exposure to infected people, and the load of virus (and infectiousness of the variant) to which they are exposed." 

In other words, being in close proximity to infected people, and being exposed often to the virus, is more apt to lead to an infection regardless of vaccination.

"Everything from someone's degree of exposure and the infectiousness of their variant to the specific workings of their immune system can impact things," Sommer cautioned. "Vaccination dramatically reduces risk of infection and severity of disease, but does not guarantee against it." 

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How frequently should I be tested for COVID-19 after being vaccinated?

Sommer pointed out that if you are fully vaccinated, there is no reason to be regularly tested for the presence of the virus unless you are experiencing COVID-19 symptoms. In addition, if you begin experiencing those symptoms, you should take precautions not to potentially infect others despite the fact that their vaccination means they are less likely to have the disease.

Finally, they need to make sure they get the right kind of test, Sommer said. That's because an antibody test will reveal the presence of antibodies, a result of vaccination. "Any test they get must test for the presence of the virus," Sommer explained.

What activities can people safely resume after being vaccinated?

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Dr. Georges Benjamin, executive director of the American Public Health Association, told Salon by email that people can take baby steps toward resuming normal life, but still need to be very careful.

"People who are fully vaccinated can be around small groups of others that are fully vaccinated," Benjamin explained. "Mask wearing is still recommended when you are around people not in your usual group or large groups that even when all are fully vaccinated. This may change when we get a better understanding of the risks of infection and transmission amongst vaccinated people."

Redlener said that life is gradually returning to normal, although like Benjamin he urged caution.

"With the caveat that there should be no relaxation of public health protocols, like masking and social distancing, we will soon soon see more people traveling, attending events — think concerts, sporting events and theater," Redlener said. "Also, small gatherings of family and close friends indoors without masks is permissible now if everyone is vaccinated and the amount and time of contact is limited."

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Gandhi expressed optimism.

"They can safety resume all activities after being vaccinated but should maintain masks and distancing in public spaces to be polite to others who are not vaccinated and also because some places in our country still have high rates of circulating cases," Gandhi explained. "As Dr. [Anthony] Fauci said yesterday, 'The vaccines protect you, so go get vaccinated — that's the message.'" She added that Fauci said if you've been fully vaccinated and are around other vaccinated people, "you shouldn't worry about it at all. Zero."


Matthew Rozsa

Matthew Rozsa is a staff writer for Salon. He holds an MA in History from Rutgers University-Newark and is ABD in his PhD program in History at Lehigh University. His work has appeared in Mic, Quartz and MSNBC.

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