Pfizer dose provokes ‘strong’ immune response in previously infected

People previously infected with coronavirus had a strong immune response after receiving only one dose of the Pfizer vaccine, opening the debate as to whether one dose may provide enough protection for this group

It also shows that not having detectable antibodies after recovering from the virus does not necessarily mean that protection is lost.

The study, conducted by Bar-Ilan University and Ziv Medical Center was published Thursday in the journal Eurosurveillance. It showed that 17 Ziv staff members who were infected with the coronavirus anytime between one and 10 months prior to vaccination developed or showed increased antibodies regardless of whether or not they had detectable antibodies against the virus before.

In total, 514 Ziv staff members participated in the study, though the majority of them had not been diagnosed with the virus.

Antibody levels of all participants were measured before and after vaccination.

“This finding can help countries make informed decisions regarding vaccine policy,” said Prof. Michael Edelstein of the Azrieli Faculty of Medicine at Bar-Ilan, who led the study. He also said that it opens the debate as to whether one dose of the vaccine may suffice – at least for the 107 million people worldwide who were previously infected.

“In some countries, this will be a very important question,” Edelstein added. “In countries where they don’t have enough vaccines, they could vaccinate more people with just one dose.”

Edelstein stressed that he is not advocating one dose for people who never had coronavirus.

The United Kingdom has been working to inoculate everyone over 70 as well as frontline healthcare workers with at least one dose of the Pfizer vaccine by sometime this month. Britain also chose to stretch out the time between vaccine doses from the 21 days recommended by Pfizer to up to 12 weeks with the goal of giving at least one dose to more people, more quickly.

Edelstein said that Britain is also not advocating only one dose, but for delaying the second dose.

Israel has continued to follow the Pfizer protocol.

Israel has had more than 710,000 Covid-19 cases. So far, nearly 3.7 million Israelis have received at least one dose of the vaccine.

The Bar-Ilan/Ziv study included Jews, Arabs and Druze. The immune response was similar across ethnicities.

Edelstein did emphasize that this is only a preliminary study of a small group and that more research would need to be done before drawing definitive conclusions.

“It is too small to bring definitive answers,” Edelstein said, “but it raises interesting questions that need to be answered with bigger studies.”