Study shows previously infected people may only need one COVID-19 vaccine dose

MILWAUKEE (CBS 58) -- Some researchers are finding people who have been infected with SARS-CoV-2 have equal or higher antibody levels after just one dose of the vaccine than people who haven’t had an infection but have gotten two doses. Doctors say this data is something that should be taken seriously, because it could mean only requiring one dose for people who have recovered from COVID-19.

“It’s exciting, because maybe that means we can rewrite the rules of vaccinating some of these people,” said Dr. William Hartman, principal investigator for UW AstraZeneca COVID-19 vaccine trial.  

The study by Icahn School of Medicine at Mount Sinai in New York City found antibody levels in people previously infected were 10 to 20 times higher than people who haven’t had COVID-19, just after the first dose.

“In a person with a previous Covid infection, when they get that first shot, that could act as the boost that we typically see with a second shot,” adds Dr. Hartman.

After the second dose, people with pre-existing immunity had more than 10 times the average antibody concentration than people without that immunity.  While the data is yet to be peer-reviewed, Dr. Hartman says the results makes sense.

“The fact that people are developing such a strong response after that first shot tells you that their immune system was already ready for the virus,” Dr. Hartman said.

“The science so far has really focused on two doses,” says Dr. Ben Weston, an associate professor at the Medical College of Wisconsin and medical director at Milwaukee County Office of Emergency Management.

Doctors say more research needs to happen to better validate the study and to know whether one dose would be sufficient for some people.

“People have seen it done once and so now we just have to have repetition of that and replication of that data,” Dr. Hartman adds. “I think some more follow up has to be done. We have to see if this holds out over a larger population.”

“It’s probably worth looking deeper into one dose versus two doses, but the science is not terribly clear right now on which is more beneficial on a broad scale,” Dr. Weston said.

Dr. Hartman says if people previously infected end up with overwhelming antibody levels after just one dose, they may not even need boosters for new variants, but that still needs further investigation.

The study says changing the rules to only one dose of vaccine for previously infected people would not negatively impact their antibody levels, while also freeing up many urgently needed vaccine doses.

“That would certainly be the hope, that there would be more vaccine available to go to more people, more quickly,” says Dr. Hartman.

Doctors say in all of this it’s important to remember natural immunity built after a COVID-19 infection varies, which could play a factor.

“Quite variable immunity, if you have a mild infection depending on your immune system you may have strong immunity, you may have long-lasting immunity or you may have weak immunity and short-lasting immunity,” Dr. Weston said.