The new mRNA vaccines for COVID-19 are highly effective at giving people immunity against the disease. But as with all other vaccines, that immunity is not 100% for everyone who receives them.
“Vaccines prevent you from getting the full form of the disease most of the time, but they don’t prevent infections entirely,” said Donald Murphey, MD, pediatric infectious disease specialist at Dell Children’s Medical Center in Austin and a member of the Texas Medical Association’s COVID-19 Task Force.
“They boost the immune system to where your immune system knows what that germ looks like and is ready to respond to it,” he said. “But that doesn’t mean that germ can’t cause a very mild infection [in a vaccinated person].”
Patients should remember two important things about these “breakthrough” infections – so named because the illness breaks through the defense created by the vaccine, Dr. Murphey says.
First, vaccinated people who get a breakthrough infection have a lower risk of developing severe symptoms than unvaccinated people.
Second, severe breakthrough infections are rare, statistically speaking. Studies about hospitalization or death tied to breakthrough infections for COVID-19 vaccines remain incomplete and are complicated by the emergence of the delta variant, according to the Centers for Disease Control and Prevention. But “vaccine breakthrough infections occur in only a small fraction of all vaccinated persons and account for a small percentage of COVID-19 cases,” CDC stated in a May 2021 report.
The way to prevent breakthrough infections is simple: More people need to be vaccinated against COVID-19, Dr. Murphey says. That is the only way to reach “herd” or “community” immunity – the point at which so many people are vaccinated that a disease finds it difficult or impossible to spread.
Because the delta variant – now the dominant strain of COVID-19 in the U.S. – spreads so fast, at least 80% of the population would need to be vaccinated, according to the Infectious Disease Society of America. At this writing, about 52% of Americans and 56% of Texans were fully vaccinated.
“We know how we get through epidemics, and that’s to get everybody immunized,” he said.