Changes to your menstrual cycle? Sore eyes? We asked a doctor about ‘strange’ COVID vaccine side effects

Did you get your COVID vaccine? (Pexels stock image)

If you received your COVID-19 vaccine, you likely knew about what to expect in terms of side effects: Perhaps a mild headache, chills or body aches, a slight fever, a sore arm or maybe a bit of fatigue.

Some people are known to experience mild and brief side effects after one or both of the shots.

Other people don’t experience these at all. Side effects, by the way, are normal signs that the body is building protection against an illness, doctors and medical experts have said.

In a May report, we asked you, our readers and viewers, if you saw any side effects from the vaccine that you weren’t expecting -- or if you experienced anything you’d never heard of before.

Read the story here, and there's still time to participate, if you'd like!

For example, I experienced a metallic taste in my mouth -- almost as if I had swallowed a bunch of nickels or pennies. It went away after about 24 hours, and wasn’t much of a bother. I debated whether it was from the vaccine, and I guess I’ll never truly know. But it did set in directly after I received my second Pfizer dose, as in, within about an hour of the shot, so it felt connected, in my book (and for what it’s worth, I just write occasional health stories. I’m not a medical expert).

Anyway, I learned I wasn’t alone. At last check, at least 98 responses in our survey mentioned the same phenomenon, following one or both shots. This NBC report made me feel a little more validated, as well. Then, my menstrual cycle was thrown off. That was another common theme seen throughout the survey. About 70 responses mention missed periods, late periods, heavy periods or some change to their cycle -- and there were occasional “my friends had this, too!” types of answers.

We had nearly 1,100 surveys completed, total.

So, I had to ask a doctor, regarding some of the more common themes seen across the survey. Could these side effects be connected to the vaccine, or could they be coincidental? Is there any cause for concern?

Dr. Matthew Sims, an infectious disease expert and Beaumont Health System’s director of infectious disease research, weighed in. He started by talking about stress, and the impact that can have on our health.

“For a lot of people, getting this vaccine is a stressful thing,” Sims said. “COVID itself is a stressful thing. For me, getting this vaccine was nothing but a relief.”

I’ll admit, I felt the same.

He went on, saying that if you poll enough people, you’ll find a good mix of results.

“The studies (on the vaccines), when they were done, followed people and looked for patterns. How many people in the placebo group experienced this, versus how many people in the treatment group saw that,” Sims said. “None of these (unusual side effects), as far as I know, in these large groups, appeared -- or if they did, there was no difference between the treatment group and the placebo group.”

Sims is referring to the treatment group, which received the COVID-19 vaccine in trials, vs. the placebo group, or the control group, which didn’t receive the vaccine. Read more about those terms here, if you’d like a refresher.

Sims and I chatted about that metallic taste, changes to the menstrual cycle, strange effects in the eyes and swollen lymph nodes, to name just a few side effects.

Let’s dive into …

That metallic mouth phenomenon

For what it’s worth, there are a number of medications that can make your mouth taste metallic, Sims said.

Sims hadn’t heard of the metallic sensation when we spoke, but said it doesn’t send up any red flags or seem alarming -- especially when I told him I only experienced it for about a day, tops.

“It’s nothing I would consider a serious side effect,” Sims said.

Eye issues

About 40 people reported burning eyes, eye pain, twitching, spasms, itching, worsened eyesight, inflammation or light sensitivity.

Although he couldn’t speak for all of these, Sims said twitching actually wouldn’t be unusual.

In fact, there’s a syndrome in which people get muscle twitches and eye twitches: It’s called benign fasciculation syndrome. And about 90% of people with this syndrome are in health care, because it’s typically nurses and doctors who notice the symptoms. The twitching tends to get worse when people are under stress.

“I have it, and I first noticed it as a medical student,” Sims said. “My muscles or eyes would twitch if I wasn’t sleeping well. It’s a little more stress-related. Stress will bring it out.”

It’s benign, so it’s not a harmful condition. But this goes back to the idea that the twitching could just be something people are noticing, post-vaccine, and it could be stress-related.

Sims isn’t saying benign fasciculation syndrome is absolutely what’s causing the twitching, but it’s possible.

Changes to the menstrual cycle

Sims hadn’t heard of this as a possible side effect, but said, again, any kind of stressor can change the period.

“Stress is the most common cause of changes to the menstrual cycle, outside of pregnancy,” Sims added.

We had all sorts of reports on this one, including two women who said they’d gone through menopause, and then got a period, post-vaccine.

Sims wanted to reiterate, if people are nervous about fertility tied to the vaccine, there’s “nothing there,” meaning, the claim is baseless. There is currently no evidence that any vaccines, including COVID-19 vaccines, cause fertility problems.

Swollen lymph nodes

It’s not clear why this side effect seemed to slip under the radar, because dozens of people reported it in our survey, but Sims said, on the contrary, this is well-described by the Centers for Disease Control and Prevention. It’s why doctors advise against mammograms immediately following the vaccine.

It’s a known reaction, because it’s a sign of your immune system responding, Sims said.

“It’s not super common, but it happens,” he told us. “If you were to look at imaging, maybe it’s that everyone gets a little swollen, but some people get a lot swollen.”


Sims reiterated, “The things you’ve mentioned, were not things we’re seeing particularly in the studies. Or if they were, they were equal between (placebo and treatment) groups.”

He added, again, often times, things caused by stress will be equal in both groups. Sims said not to listen to the vaccine naysayers.

Consider, for example, the claim of increased death after the vaccine.

“You have to think about what’s happening. The CDC will track down side effects or events that look significant,” Sims said. “The CDC has looked into reports of increased death, and they’re just not there.”

There have been people who’ve died within a week of getting the vaccine, but when the vaccine was made available, health officials started with people ages 65 and older, and the health care population.

Regarding those older people, if you took 1 million people ages 65 and older (and studied them, vaccine or no vaccine), there would be a certain number that would die the next day. And the day after that and the day after that, Sims said.

“When you start by vaccinating the older and sicker populations, like the elderly and people in nursing homes, you might see a higher mortality rate,” Sims told us. “But when the CDC compared the death rate of people who just got the vaccine versus others, it wasn’t like there were extra deaths noted in the people who got the vaccine.”

We also spoke about the nearly 1,100 survey responses. It sounds like a big number, and it is, compared to the 40, 60 or even 300 people who typically fill out one of my Google Forms.

But it’s just 1,100 out of the millions of people in the country who’ve been vaccinated.

An idea we discussed was, how much of these side effects are linked to the vaccine, and how much is happenstance? Sims had a strong example from his own experience.

“When I got the second shot, my arm hurt, but generally, I felt fine,” he said. “A little over a day later, I got super lightheaded and tired. Was I tired because I needed sleep, or was I extra tired? I lied down and kind of got some spinning. I felt like, ‘This is bad.’ But I went to bed, woke up in the morning, and it was gone. I’m assuming it was from the vaccine. But I’ve been lightheaded other times.”

Sims heard about others reporting lightheadedness as a side effect of the vaccine.

“I had some other things pop up around that time,” he added. “I heard other people’s stories and thought, maybe it was, maybe it wasn’t.”

Sims mentioned some similarities with the flu shot, in how people are talking about the vaccine.

“The flu shot can’t give you the flu,” he said. “There’s no live virus in it. And you’re not protected from the flu until two weeks after you’ve gotten your shot. So (if) you were infected a week later, perhaps you already had the flu when you were getting your shot. Maybe you got it a few days later. But all you’re going to remember is, ‘I got the flu shot and then I got the flu.’”

But is that accurate? Not really. Plus, when do doctors and pharmacies administer the flu shot?

Flu season, so influenza is usually already going around.

“It’s the same thing if someone gets the vaccine and (sees a side effect or has an adverse reaction) … when something happens in temporal proximity to a vaccine, it’s an assumption that it’s from the vaccine, but it could just be a coincidence,” Sims said. “That’s why these tracking systems track a lot of data, and we have people who analyze that data.”


About the Author:

Michelle is the Managing Editor of Graham Media Group's Digital Content Team, which writes for all of the company's news websites.