Why this Bay Area expert says not to worry if your 2nd COVID-19 vaccine is delayed

Unsure when you’ll receive the second dose of the COVID-19 vaccine?

Vaccine shortages have led Sutter Health to cancel second dose appointments across its network, leaving Sonoma County residents frustrated and confused. But there’s no reason to panic if you’re unable to receive the second shot within the Centers for Disease Control and Prevention’s recommended time frame of 42 days, said Dr. John Swartzberg, a UC Berkeley infectious disease expert.

“The reason I say that is based on how the immune system works, a booster shot works quite a long time after the primary vaccine,” he said.

Typically, two doses of the Pfizer vaccine are given 21 days apart and the Moderna vaccine is given 28 days apart. Because long-term studies on the vaccines haven’t yet been completed, the vaccine is being administered within the shortest interval possible, Swartzberg said.

“A year from now, we’re going to have good data that shows it’s probably fine to wait a few months,” he said. “We just don’t have the data.”

That doesn’t mean the vaccine won’t be effective if the doses are given more than 42 days apart, he said. One dose of the Pfizer vaccine has about 52% efficacy and one dose of the Moderna vaccine has about 80.2% efficacy. The second dose will boost your immunity to COVID-19, even if you’re forced to wait a few extra weeks.

Some vaccines are most effective when the first and second doses are given months apart, so it’s unnecessary to restart the vaccine process if your shot is delayed. The best thing to do is take the second dose as soon as it’s available.

“I believe we should follow (CDC guidelines), but if you cant do it, there’s no reason to feel a sense of ’Oh my God, I’ve been cheated out of something,’” Swartzberg said. “Once you get that second shot, you’ll have a good response.”