A recent CDC study found that messenger RNA (mRNA) vaccines appeared to be up to 90% effective in preventing COVID-19 infection in real-world settings. The study, which was released in Morbidity and Mortality Weekly Report — an online journal published by the Centers for Disease Control and Prevention — followed nearly 4,000 essential workers in the United States.
“When the mRNA vaccines were granted approval for emergency use, some people were unsure about the effectiveness outside of the research setting” says Jennifer Veltman, MD, chief of infectious diseases at Loma Linda University Health. “This real world data shows that the mRNA vaccines are indeed effective for everyday people.”
However, we also know that the vaccine is significantly less effective in the immunocompromised population, so Veltman says it’s crucial for healthy people to get vaccinated to protect those who are vulnerable.
“The study includes essential workers, some of which were immunocompromised, which likely explains why the efficacy was slightly lower than the research studies, as the research studies did not allow immunosuppressed patients to participate and in ‘the real world,’ everyone is offered the vaccine," she says. "We know that the vaccine is less effective in immunocompromised populations, but a 90% efficacy rate is still extraordinarily high.”
Clinical trials provide information on the virus at a specific time, and by the time the vaccine is provided to the general population, the prevalence of the virus might have been altered. “New variants may change the real-world effectiveness of a vaccine, but the vaccines have been shown to significantly reduce the risk of transmission and so far seem to be holding up against the emerging variants,” Veltman says.
No vaccine is 100% effective, so Veltman says there will always be some risk of transmission. “We’ve seen the number of infections drastically decrease as more of the population has been vaccinated, so we still encourage people to get the vaccine if they haven’t already,” she says.
“We hope people will take comfort in the research that continues to show the vaccine as being safe and effective at keeping our communities healthy and strongly encourage each member of our community to be vaccinated to protect those in our midst with compromised immune systems.”