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While COVID-19 vaccine supply issues have left thousands of San Diegans in limbo between their first and second doses, local researchers say there is no need to worry about receiving your second vaccine late.
What’s more important is coming back for that next appointment once it’s available, says Dr. Mark Sawyer, an infectious disease expert at Rady Children’s Hospital who has served on the advisory boards of the Food and Drug Administration who reviewed the safety and effectiveness of Moderna, Pfizer, and Johnson & Johnson Vaccines.
“People don’t have to worry about their first dose being wasted if they have to wait five weeks, or six weeks or seven weeks between the first and second dose,” Sawyer said. “It will always work and they will be protected.”
About 307,000 San Diegans who have received a COVID-19 vaccine still need a second dose, according to the county scorecard, because it takes two injections of the Moderna and Pfizer vaccines to maximize immunity to the coronavirus. And although the Centers for Disease Control and Prevention recommends that you get vaccinated within six weeks of the first one, this won’t happen for some residents due to a severe shortage of biotechnology vaccines from Massachusetts Moderna.
During the county’s weekly coronavirus briefing, officials said ongoing vaccine supply issues remain unresolved. And while local COVID-19 numbers move in the right direction, with 352 coronavirus infections and 17 new hospitalizations reported on Wednesday, recent progress will not be guaranteed until the vast majority of San Diegans have been vaccinated.
“It’s a struggle. It’s very difficult, ”County Supervisor Nathan Fletcher said. “I know this creates frustration.”
It also creates confusion for people who are wondering if they will have to start the entire vaccination process again due to a delayed second dose.
The short answer? No.
“If the second dose is given beyond these intervals, there is no need to restart the series,” read the CDC guidelines posted in mid-February.
Waiting longer for your next dose might even help, says Dr Douglas Richman, a virologist at UC San Diego, noting that other multidose vaccines, such as measles, tetanus, and hepatitis A, often space the gaps. injections from two to six months. – sometimes longer.
“I’m not worried about the delay at all, and that can be beneficial,” Richman said. “The magnitude of response for a boost gets better the longer you wait.”
The recommended second dose timing for Moderna and Pfizer vaccines – four and three weeks, respectively – is based on clinical trials. These trials were designed to quickly test whether vaccines were safe and effective; longer differences between doses would have delayed the search for these responses.
It takes about two weeks to mount a full immune response to a vaccine, so three to four weeks is the shortest of when it would make sense to get a second dose. This response involves both antibodies – Y-shaped proteins that can coat a virus and prevent infection – and T cells, which can kill infected cells before they cough up any more virus.
Most of these immune cells will die eventually, but a few will remain in case you are exposed to the same virus again. These so-called memory cells can take a month or more to form, Richman says. Once they do, their reactivation produces a faster and stronger immune response than the first time around. That’s the whole point of getting a booster shot.
In this sense, researchers have reported that the coronavirus vaccine from British pharmaceutical giant AstraZeneca is 55% effective for people who received both doses in less than six weeks, but that the effectiveness increases steadily with longer intervals. long, reaching 82% among participants who waited at least 12 weeks. for their second shot.
And while you wait, there is plenty of data showing that the first dose offers strong short-term protection. A single shot of Moderna’s vaccine is about 80% effective in preventing people from getting sick with COVID-19, according to data submitted to the FDA.
However, it is not known how long the single dose protection lasts. And with growing evidence that some coronavirus variants aren’t stopped as effectively by antibodies, it’s still important to get your second dose as soon as you can.
“You amplify your response (and) your antibodies after the second hit, so you have a higher level. As your immune response deteriorates over time, you probably have more durability and you probably have more protection, ”Richman said. “There are a lot of good reasons for getting a second shot, no doubt about it.”
Another good reason: Current COVID-19 vaccines are extremely effective in preventing serious illness and death. The county reported 25 more coronavirus-related deaths on Wednesday, bringing the region’s total to 3,342.
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