With Covid-19 vaccine shortages and problems with slow roll out, do people who already had the virus and have fully recovered need to get the vaccine, too? And is it safe for them?
The Centers for Disease Control's guidance says even people who've had Covid can benefit from the getting the vaccine.
"Due to the severe health risks associated with Covid-19 and the fact that reinfection with Covid-19 is possible, you should be vaccinated regardless of whether you already had Covid-19 infection," according to the CDC. Here's why.
When someone is infected with SARS-CoV-2, the virus that causes Covid-19, their immune system creates antibodies, which are proteins that fight off infections and help prevent future infections from occurring. That is called "natural immunity."
(The mRNA vaccines currently available for Covid work by giving cells instructions to make a non-infectious piece of the coronavirus' spike protein. The immune system detects the copies of the spike protein and creates antibodies against it.)
At this stage, there are still lots of questions about how long natural immunity from Covid lasts and whether it could prevent reinfection, Dr. David Wohl, an infectious disease physician at the University of North Carolina, tells CNBC Make It.
Studies on people who were exposed to Covid and then recovered have shown that their antibodies remained pretty stable, and only dropped "modestly" after six or eight months. Another promising outcome: coronavirus-specific B and T cells (which work together to remember and destroy infections) also appear to increase and remain high after infection.
New research that hasn't been peer-reviewed yet found that people who have already had Covid tend to have higher antibody responses after their first dose of the mRNA vaccines than two doses of the vaccine in people who haven't had it. Some immunologists argue that people who've recovered from Covid should only need one dose of a vaccine.
"If you've had Covid-19, [a vaccine] may augment or help increase the durability, and even maybe the breadth, of your immune response against coronavirus," Wohl says.
There have been some anecdotal reports of Covid survivors experiencing more severe side effects — feeling achy, sick or even feverish — after the first dose of vaccinations, Wohl says. "That makes complete sense, and shows you that the immune system is really responding to [the virus] in a much more vigorous way," he says.
But this isn't a reason to skip the vaccine. "Vaccination is still safe after you've recovered from Covid," Fauci said in a Twitter Q&A Thursday.
It's uncommon for people who are infected with Covid to get infected again within 90 days of recovering, according to the CDC. CDC Director Dr. Rochelle Walensky said that since there's a lower risk of reinfection in this population, "you may choose to temporarily delay vaccination if you already had Covid-19," during a Twitter Q&A event Thursday.
Dr. Saad B. Omer, a fellow and spokesperson for the Infectious Diseases Society of America, and director of the Yale Institute for Global Health, agrees that if you're someone who has Covid antibodies "you can afford to wait a little bit" to get the vaccine. "In the long run, it could be risky [to not get the vaccine] because there's a higher rate of reinfection than those who go get vaccinated," Omer tells CNBC Make It.