From VOA Learning English, this is the Health & Lifestyle report.

As COVID-19 vaccinations begin, health officials around the world are watching for any problems that might develop. These side effects -- a result from taking the vaccine -- are both expected and unexpected.

Allergic reactions

Recently, two health workers in the state of Alaska experienced allergic reactions after receiving the Pfizer COVID-19 vaccine. One had a severe reaction and was hospitalized for observation. The second worker's reaction was less severe.

Britain recently reported two similar cases. The Associated Press (AP) reported that these people had serious allergies in the past. As a result, British officials have warned people with a history of severe allergies to medicines to delay getting the vaccination.

Health officials in the United States are not giving such a strong warning. Healthcare workers in the U.S. always ask people about allergies before vaccinations. Instructions for the Pfizer-BioNTech vaccine say to avoid it if you are severely allergic to one of its ingredients or already have had a reaction to it.

The U.S. Centers for Disease Control and Prevention advises people to remain under observation for about 15 minutes after a vaccination. Those with a history of allergies should remain for 30 minutes. If they have a reaction, they can be treated immediately.

However, doctors said the health worker in Alaska who had the severe allergic reaction had no history of allergies. She experienced redness in her face and difficulty breathing 10 minutes after the first shot. She will not be given a second vaccine shot. The second Alaskan worker experienced less severe signs. Her eyes became puffy, her throat scratchy, and she felt shaky or light-headed.

Allergic reactions are common with new medicines. However, observing COVID-19 vaccines for unexpected side effects is more difficult in this case.

That is because of the huge number of people who need to be vaccinated over the next year. Another difficulty is the different kinds of vaccines being used at the same time. It is quite possible that one vaccine will have different side effects than another.

The first vaccine beginning widespread use in the U.S. and many Western countries is the one made by Pfizer and Germany's BioNTech. The second vaccine from the company Moderna is expected soon.

Both vaccines were made using the same method. The U.S. Food and Drug Administration (FDA) said that huge studies of each have uncovered no major safety risks.

Dr. Jesse Goodman, of Georgetown University, used to be a top vaccine official at the FDA. He told the AP that the allergy concern "points out again the importance of real-time safety monitoring."

Health officials have several ways of observing how people react to COVID-19 vaccines. The AP said that in coming months as more people get vaccinated, health officials will create more ways to monitor reactions to the vaccines.

Flu-like side effects

Getting either the Pfizer-BioNTech or Moderna vaccine can cause some temporary discomfort. This happens with many vaccines.

In addition to pain in the arm, people can experience a high body temperature and other flu-like symptoms. These include extreme tiredness, body pain, feeling cold, and a headache. These symptoms last for about a day. But sometimes they can be severe, causing the person to miss work. Reports suggest these symptoms are more common after the second shot and more common in younger people.

COVID-19 vaccines seem to cause more of those reactions than a flu shot. In some people, the reaction is similar to one people get to the vaccine for the infection called shingles.

Coronavirus-like side effect

However, some reactions are similar to early coronavirus symptoms. This is one reason hospitals are not giving the vaccine to all their employees at the same time. They are giving the vaccines to workers in smaller groups over a longer period of time.

What about serious risks?

The FDA found no serious side effects in the tens of thousands of people involved in studies of the two vaccines.

However, sometimes rare but serious side effects happen when a vaccine is used very widely. This also happens when the vaccine did not go through exact and complete tests.

The CDC's Dr. Jay Butler warned that balancing any possible risks "with the benefits the vaccine provides in the pandemic is an ongoing process."

And that's the Health & Lifestyle report. I'm Anna Matteo.

Anna Matteo adapted this Associated Press story for VOA Learning English. Mario Ritter, Jr. was the editor.

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allergic –adj., allergy –n. related to a medical condition that causes someone to become sick after coming in contact with a substance that is harmless to most people

ingredient –n. one of the substances that make up a mixture

puffy –adj. larger than normal, swollen

scratchy –adj. painful, larger, or rougher than normal

monitor –v. to watch, observe listen or check for a special purpose, such as health, over time

discomfort –n. an uncomfortable or painful feeling in the body

symptom –n. a sign that a disease or problem is present

benefit -–n. good, helpful or healthful results