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What can you expect after the COVID-19 vaccine? Wellspan expert explains

February 24, 2021


Dr. Eugene Curley, WellSpan infectious disease physician, receives his COVID-19 vaccine.

Dr. Eugene Curley, WellSpan infectious disease physician, receives his COVID-19 vaccine.

You are scheduled for your first COVID-19 vaccine. Or you are waiting for your second vaccine. 

Should you be prepared for side effects? How common are they? Are they a reason to worry? What should you do if you experience them? 

WellSpan Health has provided more than 81,000 doses through Feb. 21. Many people have a sense of relief about getting the vaccine, but some patients also have questions about what to expect after they get the shot. 

Here are answers to some of those common questions, from WellSpan Health infectious disease specialist Dr. Eugene Curley. 

How common are side effects? 

The Pfizer and Moderna COVID-19 vaccine both can cause side effects in patients, commonly within three days of getting the vaccine. And these side effects are more common than the side effects that you might experience after, say, a flu vaccine. 

The most common side effect of either COVID-19 vaccine is pain at the injection site – 78 percent or more of all recipients report this after either the first or second dose. The next most common side effects are fatigue and headache, followed by chills and muscle pain, Curley says. 

The Moderna vaccine causes, on average, more side effects than the Pfizer vaccine, studies have shown. 

For either vaccine, the chance of experiencing most side effects increases after receiving the second dose of the vaccine. 

Why does the vaccine cause side effects? Does it mean I have been exposed to COVID-19? 

You can’t catch COVID-19 from the vaccine, Curley notes. 

“The vaccine does not contain live virus,” he says. “It is very safe.” 

A short science lesson here: Both the Pfizer and Moderna vaccines are mRNA vaccines. That means they use a copy of a natural chemical, called messenger RNA, to spark an immune response in your body. You probably have seen the image of the spiky-looking COVID-19 virus, known as a spike protein. The mRNA vaccine works to cause your body to recognize and destroy that spike protein. 

The vaccine side effects  actually are a good sign, Curley said, signaling that your body’s immune system is recognizing the virus and ramping up to protect you from its effects. 

And that is why you may have a stronger reaction to the second dose of COVID-19 vaccine than the first. 

“Your body has been primed by the first dose and is ready to attack the virus,” Curley says. “Your heightened immune system then responds, producing the heightened symptoms.” 

Why do some people have side effects and others don’t? 

Side effects generally are more common in younger adults, who have stronger immune systems. 

Howeverit is important to note that many people experience only mild side effects or none at all, Curley saysIn fact, studies showed less than 17 percent of recipients reported a fever with either the Moderna or Pfizer vaccine after even the second dose, and less than half reported chills muscle pain or joint pain. Rates were even lower for vomiting. 

“If you experience only slight or moderate side effects, don’t worry that there is something wrong with your immune system, Curley says. 

The trials showed that people who received the vaccine – including older adults – produced adequate amounts of antibodies to both vaccines, with an overall 94 percent efficacy in the Moderna vaccine and a 95 percent efficacy in the Pfizer vaccineabout two weeks after getting the vaccination. 

So, what should I do if I experience side effects? When do I know to reach out for help? 

Side effects usually go away on their own within a week. If symptoms are more severe or do not go away after a week, call your primary care provider, Curley says. 

There also are some at-home remedies you can try to treat the side effects. If you have pain at the injection site, try an over-the-counter pain reliever such as acetaminophen or ibuprofen, or apply ice or a cold compress. Exercise your arm – even considering getting the vaccine in your dominant arm to ensure you are moving it around, which can make it feel better. Overall, rest and drink fluids. 

“Side effects are fleeting. Getting the vaccine is something to celebrate, not fear,” Curley says. “But remember to continue to take precautions – masking, social distancing and handwashing – as we wait for more people to get vaccines and see what happens with the virus as time goes on. Things are getting better, and the vaccine is an important step.” 

For more information about the COVID-19 vaccine, go here.