None of the trials conducted on the Moderna and Pfizer-BioNTech vaccines tested them on people who already had been infected by the coronavirus. Now, a study involving people previously infected with COVID-19 suggests the immune response from getting sick may act like getting a first dose of those double-shot vaccines.
Researchers from the University of Maryland School Of Medicine believe their findings may help inform decisions for how to make the most of limited vaccine supplies.
“With a single dose, the health care workers who previously had had COVID had a really strong response,” said study co-author Dr. Anthony Harris, professor of epidemiology and public health at the University of Maryland School of Medicine.
The immune response of previously-infected people was similar to the response typically seen on a second dose of vaccination.
“That strong response would suggest that in a time of vaccine shortage, maybe those would be the people who should get a single-dose vaccine,” he said.
A second evidence-based suggestion is that if vaccines are scarce, people who’ve already had COVID-19 could be moved lower on priority lists according to Harris and study co-author Dr. Mohammad Sajadi, associate professor of medicine at U.Md.’s school of medicine, a physician-scientist at the Institute of Human Virology and a member of the Global Virus Network.
Harris also notes that a just-released study from the United Kingdom suggests that the immune response after being sick with COVID-19 protects people for at least six months.
The practice of withholding second dose booster shots already is happening in Canada and the U.K. where Harris believes the science behind the vaccine’s trials combined with the science behind his study’s data can be helpful in deploying a successful strategy within the setting of limited supplies.
“I would say if you’re already going to a single dose — go to a single dose for people who’ve already have had COVID infection and give your highest-risk population who haven’t had COVID two doses,” Harris said.
The University of Maryland study was quite small, but Harris said the findings weren’t unexpected because the way vaccines generally work is to boost previous responses.
“Even though the sample size is small — and definitely our study needs to be replicated because we only had 59 health care workers — the differences are so dramatic that statistical significance was easily achieved,” Harris said.
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