COVID-19 vaccines for kids: What if your child gets the wrong dose?

A Florida woman who took her 5-year-old son to get vaccinated for COVID-19 last month said he was accidentally given an adult dose of the vaccine.

The woman told FOX Television Stations that she wishes to remain anonymous because she’s been bombarded with messages on social media from those who oppose the vaccine after she shared her story with the media. 

"I’ve had some crazy anti-vaxxers message me and had to change my last name on Facebook. It’s just been a crazy week," she wrote in a Facebook message to FOX TV Stations.

She said she booked an appointment to get her son a shot at a local pharmacy. They double-checked with the staff to ensure their child was getting the correct dosage.

"Then he administered the vaccine and it bled a lot. Like, he was wiping the blood off of my son's arm that was dripping down," the woman said. 

"I then asked again if he was sure that was the child’s vaccine because I had never seen someone bleed so much after a shot. He assured me again that it was. We were told to wait 30 mins after because my son has some food allergies. About 15 mins after he got the shot the pharmacist came out and told me he had given my son the wrong dose," she added in her Facebook message. 

After receiving the news, she and her husband immediately scheduled an appointment with their son’s pediatrician. The child had a fever, a very sore arm and high blood pressure, their doctor told them.

A few weeks later, the woman reported that her son was on the mend and feeling better, but they weren’t given any solid information on the potential long-term effects for children getting the wrong dose of the coronavirus vaccine. 

Last month, the White House reported that roughly 900,000 kids aged 5 to 11 received their first dose of the COVID-19 vaccine in their first week of eligibility.

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Final clearance for the shots was granted by federal regulators on Nov. 2, with the first doses to kids beginning in some locations the following day.

With vaccination efforts ramping up in an attempt to finally put the global COVID-19 pandemic to an end, reports of children getting the wrong shots have been popping up — albeit sparingly in comparison with the nation’s vaccination rates. 

On Nov. 26, an Urbandale, Iowa hospital said it is implementing procedures to ensure it doesn’t repeat a mistake made during a mass vaccination event at their facility. MercyOne said in a statement that more than 100 children under the age of 12 were given the wrong dose of the Pfizer vaccine.

The hospital said the children should have received the prescribed 10-microgram dose of the Pfizer vaccine. Instead, they received 20 micrograms-- double the prescribed dose. The prescribed adult dosage is 30 micrograms.

The hospital said children who received the higher dosage could experience more pronounced side effects, including a sore arm, mild fever, headache and fatigue.

On Nov. 15, California health officials told parents a total of 14 children received the incorrect dose of the Pfizer vaccine, in Antioch, a city roughly 44 miles East of San Francisco.

Dr. Jimmy Hu, chair of the Sutter Health COVID-19 Vaccine Task Force, wrote in a statement to KTVU that as soon as they learned about what had happened, parents were contacted and advised of guidance from Centers for Disease Control and Prevention for the situation. 

"According to the CDC, patients who receive a vaccine with an incorrect diluent volume may experience more arm soreness, fatigue, headache, or a fever in response to the dose given," said Hu.

RELATED: Sutter Health gives 14 pediatric patients wrong dose of COVID vaccine

Health officials have assured parents that there are no long-term harmful effects of getting an incorrect dose of the vaccine.

Should you be concerned if your child gets the wrong dose of the vaccine?

According to Kawsar Talaat, a vaccinologist at the Johns Hopkins Bloomberg School of Public Health, parents don’t need to panic if their child should receive the wrong dose of the coronavirus vaccine by mistake.

Talaat explains that when vaccine scientists develop the correct dosage when creating a vaccine like the one used for COVID-19, researchers typically start with a smaller dose and work their way up.

"We work up until we find the dose that is safe, but also gives us the best immune response," Talaat said. 

But Talaat says she understands why parents would be alarmed. She has a 10-year-old who recently got vaccinated. 

She recommends parents do their due diligence and ask a pharmacy clerk or pediatrician to make sure the shot their kids are getting is from a pediatric vial which is marked differently than the ones for adults. 

But even if your kid does get the wrong shot, Talaat says most side effects resolve after a day or so.

"The only consequence is you might have a little bit more side effects initially," Talaat explained. 

She says during the vaccine trials, people who got the highest possible dose reported having more of a sore arm, more fatigue or more fever very early on, but after a day or so, their symptoms tended to resolve. 

"The biggest consequence is you have a little bit more side effects but they tend to be short-lived," Talaat said. "Be careful, ask questions, but I don’t think it’s something you really have to worry about."

Why do kids require smaller doses?

The simple answer is that children have more robust immune systems. Talaat says adults over 60 may require a higher dose of the vaccine because they may have weakened immune systems, compared to that of a child. 

Despite having stronger immune systems, vaccines still help children, who have very much still been victims of this deadly pandemic. 

A study published by Pfizer in October found that kid-size doses of the Pfizer-BioNTech vaccine were 91% effective at preventing symptomatic COVID-19. The 5- to 11-year-olds developed virus-fighting antibodies as strong as those of teens and young adults who got regular doses, with similar or fewer annoying reactions such as sore arms, fever or achiness.

Very rarely, teens and young adults given the Pfizer vaccine or a similar one made by Moderna experience a serious side effect, heart inflammation, or what doctors call myocarditis. It’s mostly in young men or teen boys, and usually after the second dose. They tend to recover quickly, and after intense scrutiny, U.S. health authorities concluded the vaccine’s benefits outweigh that small risk.

To put the risk in context, COVID-19 also causes heart inflammation, often a more severe kind, said Dr. Matthew Oster, a pediatric cardiologist at Emory University. It also sometimes occurs in children who get a multisystem inflammatory syndrome after a coronavirus infection.

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Before the pandemic, doctors regularly diagnosed heart inflammation caused by bacterial or viral infections or medications, again mostly in teen boys and young men. Oster said one theory is that testosterone and puberty play a role, which is partly why many experts expect any vaccine-related risk would be lower for younger kids getting a smaller dose.

The Associated Press contributed to this story.