Pfizer booster causes similar side effects to second dose

Most people who have received a booster dose vaccine from Pfizer Inc.-BioNTech SE had similar or less side effects compared to after the second dose, according to a preliminary study from Israel’s largest health services organization.

Of the 4,500 respondents, 88% said they felt ‘similar or better’ than their reaction to the previous dose, while 31% said they had localized effects such as pain or swelling at the puncture site, according to a statement released by Clalit Health Services Sunday night.

About 15% of people had other symptoms such as fatigue, muscle pain or fever.

Less than 1% reported shortness of breath or chest pain.

Israel has become the first country in the world to widely distribute booster vaccines in an attempt to stem a wave of new cases. The United States has not yet sanctioned the use of third doses, although Pfizer announced plans to meet with U.S. regulators to obtain clearance. So far, around 500,000 Israelis have received the third dose.

Clalit said the results of the study, which involved people vaccinated between July 30 and August 1, still had to be analyzed “carefully” given the short trial period. Some people who received the boosters may have experienced significant side effects that prevented them from participating in the investigation, he said.