Why do some people feel a strange arm twitch after getting the COVID-19 vaccine?

Did you feel a strange shock in your arm several minutes after getting your COVID-19 vaccine?

While many people are prepared for a range of side effects post-vaccination, there are a few lesser-known ones. 

As far as your arm is concerned, possible symptoms following a coronavirus vaccine are pain, redness, itchiness or swelling near the site of the injection. These symptoms may surface immediately and/or seven days later.

But there's one other peculiar sensation that you might not have been expecting.

Some people experience what could be described as a twitch or minor shock somewhere near the site of the injection. However, many of them say the twitch isn't painful, albeit somewhat disconcerting. 

'That's a real thing'

Dr. Davidicus Wong is a family physician in Vancouver and Burnaby and told Vancouver Is Awesome that this sensation isn't uncommon post-vaccine. In fact, he says the response may follow any type of vaccine — not only COVID-19 ones.

"That's a real thing," he said. "The shot just happens to be going into a trigger point in that deltoid muscle that will actually spasm or twitch."

Wong, who practices acupuncture and does trigger point injection, notes that trigger points are areas in different muscles "including the deltoid where we give the shot."

Should you be concerned? 

Wong said the response is quite normal and there isn't any reason to be worried. 

The BC Centre for Disease Control (BCCDC) has provided a document for COVID-19 Vaccination Aftercare that outlines other possible symptoms as well as how to manage them.