Every sniffle, headache, rash and dizzy spell is acutely noticed by those experiencing a post-coronavirus vaccination reaction.

The general public has also been paying attention to vaccine reactions partly because the performance of the vaccines, which were developed in record time under emergency use authorization, are being watched in real-time by public-health officials.

Four months after the first batch of vaccines were delivered by Moderna and Pfizer-BioNTech, which each developed a two shot regime, a clearer picture is developing in regards to the vaccines’ safety and effectiveness.

It is to be determined how long the two vaccines and the one-shot Johnson & Johnson vaccine provide protection, but a Pfizer study showed its vaccine is 91% effective after six months.

A study by the Centers for Disease Control and Prevention (CDC) of about 4,000 health-care workers found that the Pfizer and Moderna vaccines were 90% effective after both shots and 80% after the first shot.

Clinical trials of Johnson & Johnson’s vaccine pegged its effectiveness at 72%, and it did a particularly good job protecting against severe illness.


Washington halted the use of the Johnson & Johnson vaccine on Tuesday after federal health agencies urged the pause. The CDC and Food and Drug Administration did so after six women who had received the Johnson & Johnson vaccine developed a rare blood-clotting condition. It isn’t yet clear if the cases are connected to the vaccine, of which more than 6.8 million doses have been administered nationwide.

This week’s FAQ Friday answers questions about what to do leading up to being vaccinated and what to expect after receiving a shot.

What to know before you go?

Getting a coronavirus vaccine is no different than going in for any other vaccine shot. You will need to wear a short-sleeved shirt or layers that can be removed to reveal an exposed arm.

Cancel and reschedule if you become ill before your appointment.

Wear a mask.

Are there medications that shouldn’t be taken or other factors that should be considered before being vaccinated?

Don’t mix vaccines. The CDC says a person shouldn’t get a COVID-19 shot if they have received any other vaccination during the prior two weeks. Conversely, no other vaccine should be given to someone until 14 days have passed since their COVID-19 vaccination.

The CDC recommends speaking to your doctor if you have questions about medications interacting with the vaccine. It is suggested that over-the-counter medications such as aspirin, ibuprofen and acetaminophen not be taken before a COVID-19 shot.

What to expect after being jabbed?

A person can expect their arm to be sore and stiff after a coronavirus vaccination, much like after a flu shot. Some people experience chills, headaches and can be tired.


These side-effects might be worse after the second dose of Moderna and Pfizer and shouldn’t last more than a couple of days.

There have been reports of a rash around the injection site on the upper arm as well as rashes on other parts of the body. The rashes after the first of the two-shot vaccines shouldn’t dissuade anyone from going in for a second dose, Dr. Ester Freeman, associate professor of dermatology at Harvard Medical School, told The Washington Post.

“Even though skin reactions to a vaccine can look scary, most are not severe or long-lasting, and show us that your body likely is developing a nice strong immune response to the vaccine, which is a good thing,” Freeman says.

Do you have questions about the coronavirus that causes COVID-19?

Ask in the form below and we’ll dig for answers. If you’re using a mobile device and can’t see the form on this page, ask your question here. If you have specific medical questions, please contact your doctor.

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