Although problems with the delivery of the COVID-19 vaccine have left thousands of San Diegans in limbo between the first and second doses, local researchers say not to worry about the delay in the second injection.
What’s more important is to come back for the next appointment as soon as it’s available, says Dr. Mark Sawyer, an infectious disease specialist at Rady Children’s Hospital who served on the Food and Drug Administration’s advisory panels that reviewed the safety and effectiveness of Moderna , Pfizer and Johnson & Johnson Vaccines.
“People don’t have to worry about whether their first dose was missed if they have to wait five weeks, or six weeks or seven weeks between the first and the second dose,” said Sawyer. “It will still work and they will be protected.”
About 307,000 san diegans who received the COVID-19 vaccine still need a second dose, according to the county panel, as two doses of the Moderna and Pfizer vaccines are needed to maximize immunity against the coronavirus. And while the Centers for Disease Control and Prevention recommends taking your second injection within six weeks of the first, this will not happen for some residents due to the severe shortage of the modern Massachusetts biotech vaccine.
During the weekly county coronavirus briefing, officials said the continuing problems with the vaccine supply have not yet been resolved. And while local numbers for COVID-19 are trending in the right direction, with 352 coronavirus infections and 17 new hospitalizations reported on Wednesday, recent progress will not be safe until the vast majority of San Diegans have been inoculated.
“This is a fight. This is very difficult, ”said County Supervisor Nathan Fletcher. “I know it creates frustration.”
It also creates confusion for people who wonder whether they will need to start the whole vaccination process again due to a second delayed dose.
The short answer? Do not.
“If the second dose is administered beyond these intervals, there is no need to restart the series,” says the CDC guidelines published online in mid-February.
Waiting longer for the next dose may even be helpful, says Dr. Douglas Richman, a virologist at the University of California at San Diego, noting that other multidose vaccines, such as measles, tetanus and hepatitis A, often miss vaccines in two to six months. – sometimes more.
“The delay doesn’t worry me at all and can be beneficial,” said Richman. “The magnitude of the response to an impulse improves the longer you wait.”
The second recommended dose for Moderna and Pfizer vaccines – four and three weeks, respectively – is based on clinical trials. These tests were designed to quickly test whether vaccines were safe and effective; longer intervals between doses would have delayed the discovery of these responses.
It takes about two weeks to build up a complete immune response to a vaccine, so three to four weeks is the shortest end of when it would make sense to receive 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 expelling more viruses.
Most of these immune cells will eventually die, but some remain if you are exposed to the same virus again. These so-called memory cells can take a month or more to form, says Richman. Once they do, reactivating them produces a faster and stronger immune response than the first time. This is the objective of obtaining a booster injection.
Along with these lines, the researchers reported that the coronavirus vaccine from the British pharmaceutical giant AstraZeneca is 55 percent effective for people who received both doses in less than six weeks, but that effectiveness steadily increases with longer intervals, reaching 82 percent among participants who waited at least 12 weeks for the second shot.
And while you wait, there’s a lot of data to show that the first dose offers strong short-term protection. A single injection of Moderna’s vaccine is about 80 percent effective in preventing people from getting sick with COVID-19, according to data presented to the FDA.
It is unclear, however, how long single-dose protection lasts. And with the growing evidence that some variants of the coronavirus are not so effectively prevented by antibodies, it is still important to receive your second dose as soon as possible.
“You amplify your response (and) your antibodies after the second shot, so you have a higher level. As your immune response declines over time, you are likely to have more durability and probably more protection, ”said Richman. “There are many good reasons to get a second chance, no doubt.”
Another good reason: current COVID-19 vaccines are extremely effective in preventing serious illness and death. On Wednesday, the county reported an additional 25 coronavirus-related deaths, bringing the region’s total to 3,342.