What are the side-effects of the Pfizer vaccine?

This is part 81 of our coronavirus FAQ. Click here to read other installments: #Coronavirus the facts. Find the latest information and answers from experts on everything COVID-19.


Typical side-effects from vaccines include fever and swelling around the injection site. According to Dr. Taniguchi Kiyosu, the head of the clinical research department at the National Mie Hospital, these symptoms indicate that the vaccine is working.

Japan is using the Pfizer vaccine for its coronavirus inoculation program. According to a weekly report by the US Centers for Disease Control and Prevention, of the roughly 815,000 people who had received a first dose of the Pfizer vaccine as of January 13, nearly 73% experienced pain in the site of injection. Other side-effects include: fatigue (21.9%), headache (17.5%), muscle pain (14.7%), swelling (6.2%), fever (5.8%), chills (5.5%), joint pain (5.3%), and nausea (4.2%).

In many cases, these symptoms occur one or two days after the shot and last for several days.

Cases in Japan

Japan started vaccinations in February. The health ministry has confirmed symptoms in 17,138 healthcare workers ranging in age from their 20s to 70s. The most common side-effects were pain at the site of injection (92%), fatigue (23.1%), and headache (21.3%). In rare cases, people reported experiencing serious headaches and fatigue that interfered with their daily life, and 3.3% reported a fever of 37.5 degrees or higher. These symptoms usually appeared the day following the shot.

Anaphylaxis reaction

The ministry had recorded 17 cases of severe allergic reactions by March 9. Of these, seven were confirmed as anaphylactic reactions. With 107,600 vaccines administered as of that date, this comes out to a rate of 65 anaphylaxis cases per one million shots. The rate of anaphylaxis for flu vaccines is about one per one million. Experts say anaphylaxis is not fatal if treated properly with adrenaline injections and other measures.

The health ministry says it will continue to monitor the prevalence of side-effects.