The COVID-19 pandemic has killed around 7 million people worldwide (1.1 million in the United States) and made many more people sick. Vaccines and antiviral treatments helped save many lives and reduce sickness. According to a report from the Commonwealth Fund, COVID-19 vaccines alone prevented over 18 million hospitalizations and 3.2 million deaths in the United States. But new versions of the virus (like Omicron) caused more sickness and disease in 2022 and 2023.
Aaron Carlin, MD, PhD, associate professor of pathology at University of California San Diego School of Medicine, said,
“We were worried about new waves of illness caused by BA.5, which became the most common version of the virus in the United States. It looks like getting sick with an earlier version of the virus doesn’t always protect you from getting sick again with newer versions.”
Carlin and other researchers at UC San Diego School of Medicine published a study in the March 21, 2023 online issue of Open Forum Infectious Disease. They explain how the subvariants of COVID-19 spread quickly among people who had been sick before and how the medicine Paxlovid might have made people more likely to get sick again.
The researchers found that changes in the virus’s spike protein allowed it to avoid antibodies made by vaccines or earlier infections. Also, Paxlovid treatment might have lowered people’s immune responses and made them more likely to get sick again.
Paxlovid is a medicine that combines two drugs (nirmatrelvir and ritonavir). It was one of the first medicines made for COVID-19 and was often given to people soon after they got sick. It was meant to reduce the chances of getting very sick or dying from COVID-19. Later research showed that Paxlovid treatment lowered the risk of hospitalization or death for unvaccinated people at high risk of getting very sick from COVID-19.
But Paxlovid didn’t always stop people from getting sick again.
Smith said,
“Our findings suggest that early antiviral treatment can help people avoid getting very sick from COVID-19. But people still need to get vaccinated and get booster shots to stay protected from the virus. We need to keep studying the virus and creating new medicines and vaccines to stay safe from the next pandemic.”