Low Risk of Vaccine Breakthrough Infections, Says Study

COVID-19 vaccine breakthrough infections
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In a study of 417 individuals, only two went on to develop vaccine breakthrough infections; citing the risk as extremely rare.

As vaccination efforts speed up across the world, more and more cases of vaccinated individuals contracting COVID-19 are coming forward. These cases are called breakthrough infections. Recently, the US Center for Disease Control and Prevention (CDC) reported over 7,000 vaccine breakthrough infections in the United States. However, it’s a very small percentage among more than 87 million people who have completed their vaccinations.

Vaccine breakthrough infections make up a small percentage of people who are fully vaccinated. CDC recommends that all eligible people get a COVID-19 vaccine as soon as one is available to them

CDC’s statement to CNN

Now, a study from New York further suggests that the risk of such infections is extremely low.

The team of researchers at Rockefeller University conducted the study among 417 employees who had received both doses of either the Pfizer or Moderna vaccine. According to the study published in the New England Journal of Medicine, only two of them had breakthrough infections later. Both of the patients, who developed symptoms of COVID-19, were women.

Infection Despite an Antibody Response

Patient 1, a healthy 51-year-old, developed a headache, sore through, and congestion 19 days after receiving second dose of the Moderna vaccine. PCR testing, conducted later that day, confirmed her as COVID-positive. Her symptoms gradually resolved over the course of a week.

Patient 2 was a healthy 65-year-old who developed symptoms five weeks after receiving the second dose of the Pfizer vaccine. The symptoms included fatigue, headache, and sinus congestion. Three days after testing positive for COVID-19, her symptoms began to resolve.

Further analysis of the serum samples revealed the presence of coronavirus variants within both patients. Moreover, patient 1’s sample included the E484K mutation. This particular mutation helps the virus escape neutralizing antibodies and was first found in the South African variant. Another important mutation, found in both patients, was the D614G.

Examination of the SARS-CoV-2 [genetic] sequences revealed that both patients were infected with variant viruses

study authors

Moreover, Patient 1 had high levels of neutralizing antibodies shortly after the development of symptoms. Based on the clinical history and antibody titers of both the patients, the researchers conclude that they likely had an effective immune response to the vaccines.

However, such findings should not be a cause for concern. No vaccine is 100% effective at preventing COVID-19, but they do reduce the risk of hospitalizations and death.


Hacisuleyman, Ezgi, et al. “Vaccine Breakthrough Infections with SARS-CoV-2 Variants.” New England Journal of Medicine, 2021, doi:10.1056/nejmoa2105000.


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