Another day, another weird side-effect story on the front lines of the vaccination campaign. But this time it’s not the Johnson & Johnson vaccine that’s under scrutiny. After the Pfizer vaccine was approved for everyone age 12 and up, a small number of teenage patients experienced troubling chest pains after receiving the second dose. After further diagnosis was conducted, it turned out that they had all developed inflammation of the heart muscle, a condition known as myocarditis. The good news is that none of them died or required more than a few days of hospitalization and the damage is not considered permanent. But was this a reaction caused by the vaccine or just a random coincidence? (Associated Press)

Health authorities are trying to determine whether heart inflammation that can occur along with many types of infections could also be a rare side effect in teens and young adults after the second dose of COVID-19 vaccine.

An article on seven U.S. teen boys in several states, published online Friday in Pediatrics, is among the latest reports of heart inflammation discovered after COVID-19 vaccination, though a link to the vaccine has not been proven.

The boys, aged 14 to 19, received Pfizer shots in April or May and developed chest pain within a few days. Heart imaging tests showed a type of heart muscle inflammation called myocarditis.

A small number of similar cases were reported in Israel after they began vaccinating teenagers with the Pfizer doses.

Drawing a link between these cases and the vaccine may prove tricky, if not impossible. Patients can experience myocarditis in relation to any number of infections, including COVID, but it’s unclear if any or all of these teenagers had previously contracted the disease.

Myocarditis is no more or less common in children than adults. It can occur as a side effect of a long list of viral infections including parvovirus, influenza, rubella, and HIV. But if these teenagers hadn’t contracted any such virus and no other mundane cause can be identified (such as more rare instances of bacterial infections, fungus or parasites) then researchers will need to determine if it actually was the vaccine that caused it.

Even if this does turn out to be a condition linked directly to the Pfizer vaccine (the only one approved for those under 18 thus far), it’s worth keeping in mind what a rare event this has been. As of last week, more than 2.5 million teenagers had been vaccinated. Out of those millions, only seven cases of myocarditis have been identified. And none of the patients appear to have suffered any severe outcomes. Those are still pretty good odds if you’re debating whether or not to sign your child up for a jab.

But at the same time, it can’t be stressed enough that we’re still sailing in somewhat uncharted waters here. These vaccines were developed, tested and granted emergency approval for distribution in record times that were previously unimaginable. In times past, when a new disease broke out, it would take years before any significant number of patients were able to receive a shot. And while the testing process is as thorough as the pharmaceutical companies can manage, we never learn the full range of possibilities until enough doses have been administered to cover a significant portion of the population. But if this is the worst that we see from the COVID vaccines, they’re still looking reasonably safe and amazingly effective. Breakthrough cases are still incredibly rare and the ones who do contract COVID after being vaccinated tend to suffer far milder effects.