Penn Medicine studies how long the COVID-19 vaccines last

PHILADELPHIA (WPVI) -- Government health officials issued warnings surrounding the rise in COVID-19 cases in many states as researchers at Penn Medicine reveal how long the vaccines may last.

As vaccinations got underway with the mRNA vaccines by Pfizer and Moderna, researchers at the Penn Institute of Immunology are beginning to test volunteers.

They measured antibodies that show rapid immunity and memory B cells which indicate longer immunity.

"What we were able to see is the vaccines produce really good memory B cells. Which means even if antibody levels fall lower, even if we might see variants that the antibodies may not catch well, we still have this second-tier defense," said Dr. E. John Wherry from Penn Institute of Immunology.

Wherry led the study, which is now published in Science Immunology.

Another finding, if you had COVID-19, you might get enough protection after just one dose of the vaccine, but if you escaped the virus, Wherry said you definitely need two doses.

"Really getting that second dose boosts your immune response up to the maximum level," added Wherry.

He says larger studies are needed. They're not making any recommendations now except to encourage more people to get vaccinated.

Cases are climbing in at least 20 states, 14 seeing an increase in hospitalizations. While more seniors are now protected, the majority of Americans are still unvaccinated and at risk.

Johns Hopkins epidemiology expert Jennifer Nuzzo urges continued precautions.

Our goal is to protect people long enough to be able to reach them with vaccines," she said.

One other reassuring aspect of the Penn study says if you had strong side effects from the vaccine such as fever, chills, or fatigue, you likely had a strong immune response which means the vaccine is doing what it is supposed to do to protect you.