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In-Depth: San Diego medical experts weigh-in on COVID-19 vaccine second dose delays

Posted at 6:14 PM, Feb 16, 2021
and last updated 2021-02-16 21:14:25-05

SAN DIEGO (KGTV) Scheduling a second COVID-19 vaccine dose continues to be a problem for some San Diegans.

Some second-dose appointments were even delayed by about one week when a vaccine shortage caused the Petco Park vaccination super station to close down for three days.

ABC 10News has heard from viewers, worried that they won’t get the second dose within the recommended time frame; 21 days after the first dose for Pfizer-BioNtech, and 28 days after for Moderna.

“Just because you’ve been delayed, whether it be eight days or 14 days, doesn’t mean you’re not going to respond appropriately. We believe you can respond appropriately,” said Dr. David Pride, Director of Molecular Microbiology for UC San Diego Health.

Pride says when you receive the first COVID-19 vaccine dose, your body starts working to provide protection.
“You’re really sort of trying to prime your immune system to start responding,” he said. “Most importantly, you’re trying to create in such a way that your immune system is trying to remember having seen that virus before.”

The second dose, or booster, then ramps up that immune response.

Pride said shooting for the 21 or 28 days is ideal, but if that’s not possible. He said there is some leeway.

The Centers for Disease Control and Prevention (CDC) recently updated guidance on its website to say, “The second dose should be administered as close to the recommended interval as possible. However, if it is not feasible to adhere to the recommended interval and a delay in vaccination is unavoidable, the second dose of Pfizer-BioNTech and Moderna COVID-19 vaccines may be administered up to 6 weeks (42 days) after the first dose.”

“They came up with 42 days based on data and studying the population and getting a feel for how the body mounts the immune response,” said Merissa Corey, Pharmacy Supervisor at Sharp Chula Vista Medical Center.
“There’s not a lot of data out there, but the limited data they have has said ‘if it is not feasible to get the shot at the optimal time, and it’s unavoidable, that you have up to 42 days to get the shot from the first dose without compromising your body’s immunity’.”

Both Corey and Pride agree people should strive to get the second dose within the original recommended timeframe because that has been studied the most; however, if your appointment is delayed, follow the CDC guidelines and get the second shot within the 42-day window.

“Do not be concerned you are still able to mount an immune response if you are within 42 days of your first dose. The closer to day 21 and 28, the better, but overall you have a safety margin now that the CDC has given you.”

“You’ve already been afforded some level of protection from having that first dose, continue to stay vigilant and perform your social distancing, masking, don’t travel.” said Pride. “Don’t be too disappointed because that second dose of the vaccine got delayed.”