Exactly how long does a COVID-19 vaccine last?
More information exists about Pfizer BioNTech and Moderna vaccines than the Johnson & Johnson vaccine, simply because trials of the former started earlier than those of the latter, explains Timothy Brewer, MD, professor of medicine and epidemiology at UCLA. And the data available is promising.
Recently, Pfizer announced that its vaccine efficacy remains at 91 percent for trial participants a full six months after the second dose. “That’s really encouraging news,” says Dr. Brewer. “And it doesn’t mean that the vaccine efficacy won’t last longer, it just means that’s all the data we have so far.”
Moderna also has data—albeit from a much smaller sample—that suggests lasting efficacy of its vaccine. According to Dr. Brewer, 33 Moderna trial participants maintained binding antibodies and neutralizing antibodies for up to 209 days after their second dose.
And there is some evidence suggesting six months is likely, as Dr. Brewer has noted, to be a conservative estimate of efficacy. One small study showed that people who were naturally infected with COVID-19 maintained antibodies for eight months thereafter, and because the vaccine creates more antibodies than natural infection does, it’s likely you would be protected for even longer than that after vaccination.