Your second COVID-19 shot might cause more side effects than the first — don't panic

WCPO vaccine.jpg
Posted at 6:30 PM, Jan 15, 2021
and last updated 2021-01-15 18:43:23-05

The side effects from the second dose of the COVID-19 vaccine might pack more of a punch than the first one, local health leaders confirmed Friday.

It only happens for about 20% of patients, they said, and it’s not a reason to avoid getting vaccinated, but it’s important to know what to expect when you get the shot.

“We’ve got to be honest and straightforward,” said Dr. O’Dell Owens, a longtime physician who now runs the Cincinnati health advocacy group Interact for Health. “The second shot’s a little harder on you than the first for some people.”

Reported side effects of both the Moderna and Pfizer vaccines, both of which are delivering in two doses spaced weeks apart, include aches, chills, fever and fatigue. A patient might experience any of these side effects from their first shot, but they appear to be stronger after the second.

Why? Here’s the short version.

The COVID-19 vaccine is an mRNA vaccine that teaches the recipient’s cells to make a harmless piece of the “spike protein” found on the surface of the virus that causes COVID-19. The vaccine cannot cause a recipient to develop COVID-19, but the presence of the foreign protein still triggers an immune system response.

The body produces antibodies that can fight the virus, and the patient is protected from illness without ever having to catch the novel coronavirus.

The demanding internal process of shoring up the immune system and making those antibodies is what causes most vaccine side effects, not the virus.

What's mRNA?
Good question — it's been a few years since we were in high school biology, too. mRNA is "messenger RNA," a type of molecule that contains genetic instructions for building a particular type of protein. These instructions are "read" by other cells, which create the protein in question. The RNA part stands for "ribonucleic acid," a basic building block of life. All living things need mRNA to survive.

READ MORE about mRNA vaccines via the Centers for Disease Control and Prevention

Dr. Carl Fichtenbaum of UC Health compared the immune system to a boxer. Good fighters protect themselves more ferociously after taking a punch — so do bodies that receive more than one dose of a vaccine, even when a two-dose system is necessary.

“The response is often a little bit more powerful, more vigorous and more quick,” he said. “That's why, when people get the second vaccine, many times they feel a little bit worse than when they got the first vaccine."

Dr. Phillip Hartman, a St. Elizabeth physician who received his second dose Wednesday, said he had not experienced any notable side effects.

The rate of patients who do is around 20%, and in some cases they might not feel well enough to work for a day or two. Hartman said that’s expected.

“It’s really a minimal inconvenience to where you’re going, especially when you consider I treat patients that had COVID six months ago and still aren’t breathing right,” he said.

Owens said he hopes telling people what to expect will keep them calm and knowledgeable about the process, making them less vulnerable to scare tactics or conspiracy theories.

“I’m so afraid that some people are going to say, ‘Oh, look what happened to me,’ and you won't have these people coming back on time for their second shot, and that's important,” he said.