The first US Centers for Disease Control and Prevention accounting of breakthrough coronavirus infections among fully vaccinated people shows such infections are very rare, Dr. Kawsar Talaat, an infectious disease physician and assistant professor at Johns Hopkins Bloomberg School of Public Health, told CNN on Thursday. She said it actually underscores the urgency to vaccinate more people against Covid-19.
The likelihood of these “very rare” infections depends on how much virus is circulating within a community, Talaat said. As more people become fully vaccinated, there will be less virus circulating, and less opportunity for anyone to be exposed.
“That’s the whole point of getting to herd immunity,” she said. “Because once we get to a point where enough people in the community are vaccinated, then if somebody develops Covid in that community, the people around them are protected and it’s much harder for that person to spread the virus to somebody else, and therefore the transmission stops.”
About 77 million people in the United States have been fully vaccinated. In data released to CNN on Wednesday, the CDC said 5,800 breakthrough cases have been reported so far, although there is a delay in reporting. Among the reported cases, 396 were hospitalized, 74 died. The CDC also said 29% were asymptomatic.
The CDC said it’s monitoring reported cases “for clustering by patient demographics, geographic location, time since vaccination, vaccine type or lot number, and SARS-CoV-2 lineage,” and so far, no unexpected patterns have been identified.
Talaat said that, overall, the breakthrough infections tend to be much milder than the cases seen among unvaccinated people.
“It’s important to realize how many lives have already been saved by the number of people that we vaccinated so far,” she said. “The more people we vaccinate the more lives that we can save.”
Hypothetically, “you have a population where there’s 20,000 people. Half are vaccinated and half are unvaccinated. In the unvaccinated group, if 1% of those people have Covid – that’s 100 people in the unvaccinated group of 10,000 – then you would have maybe 10 in the vaccinated group,” Talaat said. “But then if at any given time the percent of people infected is .1% in the population, then those numbers go down to 10 and one.”
Some breakthrough infections are expected with these and other vaccines. No vaccine is 100% effective.
In clinical trials of the vaccines, there were a few breakthrough infections among vaccinated people, Dr. Carlos del Rio, executive associate dean at Emory University School of Medicine, wrote in an email on Thursday. Del Rio is an investigator on clinical trials for Moderna and Novovax Covid-19 vaccines.
“There is currently a lot of transmission in many parts of the country. Vaccines will help decrease that,” del Rio said in the email. “Get vaccinated as soon as you can and help control this pandemic.”
Del Rio added that in the meantime, the public needs to continue masking and social distancing to also help drive the numbers down.
