Coronavirus vaccines: Why are some countries recommending single dose for teens, young adults?

Concerns of myocarditis, an inflammation of the heart, after a second COVID vaccine dose in teens and young adults has sparked several countries to turn to a single-dose vaccination tactic for that age group instead of the double dosage, according to multiple media outlets.  

Officials in England, Norway and Hong Kong, for instance, have recommended administering a single dose of the Pfizer-BioNTech vaccine for children ages 12 and older. The effort is intended to provide partial protection from the coronavirus while reducing the risk of potential side effects, such as myocarditis, an adverse reaction occasionally seen after a second dose of one of the mRNA vaccines in this age group, according to multiple reports.  

Dr. Aaron Glatt, a spokesperson for the Infectious Diseases Society of America and professor and chair of medicine at Mount Sinai South Nassau on Long Island, New York, weighed in on the reports and told Fox News, "This new strategy is certainly worthwhile evaluating. It has theoretical and practical advantages if it works." Glatt warned, "However, the appropriate full studies to prove that this should be the standard approach remain to be performed and analyzed." 

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Health officials in Hong Kong recommended a single dose of the Pfizer-BioNTech vaccine for children ages 12-17 last month after reports of heart inflammation were seen as a side effect of the second dose of the mRNA vaccine, according to a report by Reuters.  

Professor Lau Yu-lung, who chairs a panel of health experts advising Hong Kong government officials on their vaccination program, told a local media outlet that health experts thought it was more beneficial for teenagers to receive only one dose to "greatly reduce the chance of heart inflammation," according to Reuters.

England and Norway are also recommending the single dose of the Pfizer/BioNTech vaccine to children ages 12-15 and will await a decision on second doses until further data is rolled out, according to multiple reports.  

According to the Centers for Disease Control and Prevention (CDC),  cases of myocarditis and pericarditis, an inflammation of the lining of the heart, occurred more often in male adolescents and young adults after receiving a second dose than after the first dose of the mRNA Covid-19 vaccine (Pfizer-BioNTech or Moderna).  

Those who reported having myocarditis or pericarditis responded well to medicine and recovered quickly, the CDC said on its website.  

A statement on the health agency website noted, "These reports are rare and the known and potential benefits of COVID-19 vaccination outweigh the known and potential risks, including the possible risk of myocarditis or pericarditis." 

Dr. Fred Davis, an associate chair of emergency medicine at Northwell Health in New York, told Fox News, "The CDC reports that myocarditis reporting rates were 40.6 cases per million after the second doses of mRNA COVID-19 vaccines administered to males aged 12−29 years. That is far less than 1% in this group." 

Davis, who specializes in emergency medicine, told Fox News that myocarditis remains a rare side effect of the mRNA vaccine, and that if it does occur, "Most of these cases respond well to anti-inflammatory medication and rest. Most of these symptoms resolve in one to two weeks." 

Davis also commented on those countries that recommend the single-shot tactic and told Fox News, "While the approach to offer a single dose of vaccination for children 12 and older will offer less protection (52% with one dose vs 88% with two doses of Pfizer), this approach allows more children to be vaccinated with number of vaccines at hand while also reducing the already minimal risk of side effects seen after the second dose."  

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Davis, who is board certified in emergency medicine and an associate professor at the Donald and Barbara Zucker School of Medicine at Hofstra/Northwell in Hempstead, New York, told Fox News, "This approach of a single dose will hopefully encourage more parents to realize the benefits greatly outweigh the risks and get their children vaccinated."

Meanwhile, Glatt, who is also a hospital epidemiologist, cautioned that "We also need to understand that in adults, the data clearly show that two doses are needed to get stronger immunity."