Single BioNTech jab significantly reduces myocarditis risk for teens – HKU research

Adolescents vaccinated just once with the BioNTech vaccine were six times less likely to develop myocarditis compared to their peers who had received two doses, according to a research team of the University of Hong Kong.  

The population-based cohort study compared the incidence of myocarditis in adolescents aged 12 to 17 before and after the recommended single-dose regimen of BioNTech starting from September 16, 2021.  

As of October 18, 2021, it was found that 43 out of 224,560 vaccinated adolescents experienced myocarditis-related hospitalization following BioNTech vaccination; 36 of them occurred after the second dose.  

If taken three weeks after the first dose, the estimated relative risk following the second dose is 7.11 times as high as the first dose.   

Given 40,167 adolescents whose second doses were deferred following the announcement of the single-dose recommendation, it was estimated that about nine myocarditis cases were prevented.  

Another study conducted by the team found that 305,406 doses of BioNTech vaccine were administered to 178,163 people aged 12 to 17 between June 14 to September 4 last year.  

Among them, 33 developed acute myocarditis or pericarditis - 29 boys and four girls - with a median age of 15.25 years.  

All patients had mild diseases requiring no treatment or symptomatic relief by non-steroidal anti-inflammatory drugs. They spontaneously recovered without the need for systemic steroids, intravenous immunoglobulins, inotropic or circulatory support.  

"Compared with hospital controls, it was found that BioNTech recipients had about a three-fold higher risk of myocarditis or pericarditis than the unvaccinated," the team said.  

It also said no statistically significant association of Sinovac with myocarditis or pericarditis was observed.  

Patrick Ip from the Li Ka Shing Faculty of Medicine said, "Even if adolescents receive the second dose, preliminary data from other countries have shown that the longer the dosing interval, the lower the risk of carditis."  

Mike Kwan from HKUMed said, "Based on the findings, adolescents are strongly recommended to receive the first dose of Covid-19 vaccine as soon as possible, in bid to ward off the fifth wave of Covid-19 in Hong Kong".