Five things to know about the coronavirus vaccine

Suzanne Kreiter/Globe staff

The nation was abuzz Monday with news of the first coronavirus vaccines being injected into people’s arms, which offered a ray of hope as the nation continued to grapple with a surging pandemic.

Here’s a brief refresher on what you need to know about the vaccine:

How does it work?

The vaccine, made by Pfizer Inc. and its German partner BioNTech, contains messenger RNA (mRNA), which is genetic material. The vaccine contains a small piece of the coronavirus’s s mRNA that instructs cells in the body to make the virus’s distinctive “spike” protein. “When a person receives the vaccine, their body produces copies of the spike protein, which does not cause disease, but triggers the immune system to learn to react defensively, producing an immune response” against the virus, the US Food and Drug Administration said in a Friday news release.

Dr. Anthony Fauci, the nation’s top infectious disease expert, has called the results of the Pfizer/BioNTech clinical trials “extraordinary.”

Who is allowed to get it?

The Prizer/BioNtech vaccine, which is given in two doses three weeks apart, has been approved for people 16 years of age or older.

Who should not get it?

People who get a shot and have a severe reaction should not get a second shot.

“There is a remote chance that the Pfizer-BioNTech COVID-19 Vaccine could cause a severe allergic reaction, " according to a fact sheet for patients and caregivers posted on the FDA website. The reaction would usually occur within a few minutes to one hour after getting a dose. If you experience a severe reaction, you should call 911 or go to the nearest hospital, the fact sheet says.

People who have had a severe allergic reaction to any ingredient in the vaccine should not get the shot. The ingredients are listed in the fact sheet.

Pregnant or breastfeeding women should consult with their health care providers before getting it, the fact sheet said.

Are there side effects?

Side effects are possible, including injection site pain, tiredness, headache, muscle pain, chills, joint pain, fever, injection site swelling, injection site redness, nausea, feeling unwell, and swollen lymph nodes, according to the fact sheet.

The FDA said more people felt side effects after the second dose, so “it is important for vaccination providers and recipients to expect that there may be some side effects after either dose, but even more so after the second dose.”

Why should I get it?

Vaccine supplies will be limited at first and distributed in a phased fashion. But when it’s eventually your turn, there are many reasons to get vaccinated, according to officials who are trying to overcome reluctance from some in the public.

The vaccine will prevent you from getting seriously ill from a disease that has already killed about 300,000 people in the United States. It’s not clear, officials noted, how long the protection will last.

“The totality of the available data provides clear evidence that the Pfizer-BioNTech COVID-19 Vaccine may be effective in preventing COVID-19. The data also support that the known and potential benefits outweigh the known and potential risks,” the FDA said.

Vaccines may also keep you from transmitting the virus to people around you, something that’s still being studied, the US Centers for Disease Control said. It’s safer to gain immunity from a vaccine than from naturally contracting the dangerous virus. And vaccines are a crucial tool to ultimately stop the coronavirus pandemic, in conjunction with measures such as masks and social distancing.

“Stopping a pandemic requires using all the tools we have available,” the CDC said.

Worried about safety? The approval came after “an open and transparent review process that included input from independent scientific and public health experts and a thorough evaluation by the agency’s career scientists to ensure this vaccine met FDA’s rigorous, scientific standards for safety, effectiveness, and manufacturing quality,” FDA Commissioner Dr. Stephen Hahn said in the statement.