mRNA COVID-19 vaccines: Benefits far outweigh the risk

The benefits of mRNA* COVID-19 vaccines far outweigh the very small risk of vaccine-related myocarditis, says the US Centers for Disease Control and Prevention (CDC).

“The likelihood of [vaccine-related] myocarditis is low, and most cases are mild,” the agency said. “Patients seemed to get better quickly … The risk of severe and lasting outcomes is much higher from COVID-19 [than from any vaccine] and this can be prevented through vaccination.”

“I think the most important message at this point is eligible people older than age 12 should get vaccinated,” commented Dr Jeremy Asnes, chief of paediatric cardiology at Yale Medicine, New Haven, Connecticut, US. “While we take reports of myocarditis very seriously, we – along with the CDC – continue to feel that the benefits of COVID-19 vaccination far outweigh the small risk of getting vaccine-related myocarditis.”

Small risk, million doses

Presenting data from the CDC Vaccine Adverse Event Reporting System (VAERS), Dr Tom Shimabukuro of the CDC-Immunization Safety Office, said 1,226 cases of myocarditis or pericarditis have been reported as of June 11, with 827 cases after dose two of any mRNA vaccine. [MMWR 2021;70;977–982]

“These figures are very small given the 296 million vaccine doses administered in the US – the risk equates to roughly one in 240,000 doses.” Patients generally recover from symptoms and do well, he added.

Chart-confirmed myocarditis cases from the Vaccine Safety Datalink (VSD) showed that the incidence remains rare at 4.7 cases per 1 million women and 32 cases per 1 million men after dose two. The overall rate was 12.6 cases per million, occurring within 21 days of dose two of any mRNA vaccine.

Risk for COVID complications higher

In a review paper, Dr Biykem Bozkurt from Baylor College of Medicine, DeBakey VA Medical Center, Houston, Texas, US, summarized the current evidence for mRNA vaccines and myocarditis, including the CDC. [Circulation 2021;doi.10.1161/CIRCULATIONAHA.121.056135]

She said the risk of myocarditis following vaccination is smaller (12–14 cases per million vaccinations) than the risk for COVID-19 complications (0.1–1 case per 100,000 in those aged 12–29 years).

“The risk of myocarditis appears highest among males 16–18 years old,” Bozkurt noted. “But this age group also falls within the category identified by the CDC as facing risks of hospitalization for COVID-19 infection of 183 per million, ICU admission of 38 per million, and dying of 1 per million.”

In the same paper, the CDC estimate of myocarditis/pericarditis rates was 12.6 cases per million doses of the second dose of mRNA vaccine in those aged 12–39 years. Symptoms resolved and diagnostic markers and imaging results improved with or without treatment.

Independent of vaccines, myocarditis occurs in roughly 23 per 100,000 people globally every year. [Front Cardiovasc Med 2021; 8:610989] This suggests that the risk in the general population was higher than from vaccination.

Delta – the real threat

The assurances by experts should help clear residual fears and stamp out vaccine misinformation as the highly transmissible Delta (B.1.617.2) variant sweeps across Asia.

“The biggest risk to the world at the moment is simply Delta,” said Professor Sharon Peacock, a microbiologist from the University of Cambridge in Cambridge, UK. “It’s the fittest and fastest variant of the coronavirus to date.”

Delta grows more rapidly in human respiratory tracts and spreads two to three times faster than the original strain of the coronavirus. On average, people infected with the variant had about 1,000 times more copies of the virus in their respiratory tracts than those infected with the original strain. [https://virological.org/t/viral-infection-and-transmission-in-a-large-well-traced-outbreak-caused-by-the-delta-sars-cov-2-variant/724, accessed 26 July 2021]

The Delta variant is pushing cases in under-vaccinated hot spots in the US and prompting further waves of infections in Asia.

Indonesia reported over 54,000 new cases and 991 deaths in a single day in July, making it the epicentre of the pandemic in Asia. Malaysia recorded 17,045 new cases on July 25, setting a new record for the third consecutive day.

In Singapore, 129 new COVID-19 cases were reported on July 26, of which 61 were linked to the Jurong Fishery Port cluster and 6 traced to KTV clubs. The growing cases set off alarms in the island-state, which had gone from zero to a record high of 182 local transmissions on July 20, prompting a  revert to phase two (heightened alert) measures, including a nationwide dine-in ban until Aug 18.

Vietnam, Thailand, and South Korea have all imposed new lockdown restrictions in July due to rising COVID-19 cases. In the US, the Delta variant now accounts for an estimated 83 percent of all sequenced COVID-19 cases.

An elusive dream

The surge in cases has brought back déjà vu and new restrictions, leaving many in utter dismay. The situation could have been largely prevented if more people were taking the vaccines in countries where these are accessible. Where there is vaccine hesitancy, herd immunity is stalled. And without enough numbers of vaccinees, herd immunity remains an elusive dream.

In the words of WHO Director-General Tedros Adhanom Ghebreyesus words, “the pandemic is far from over. It will not be over anywhere until it is over everywhere.”

So, get yourself vaccinated and do your part.