benefits of Covid Vaccines

The short version: the COVID vaccines clearly reduced severe disease and death in older adults during the first waves, but the evidence for younger, healthy people is much thinner, and the safety data on myocarditis in young males is real and dose-dependent.

The strongest evidence comes from the early rollout when vaccines were given to the oldest and sickest first. A UK modelling study found that vaccinating people over 80 reduced deaths by 62% and hospitalizations by 33% in that group alone [2]. A Tennessee study showed older adults had a 95% lower death rate and 80% fewer hospitalizations after vaccination [7]. A Hungarian nationwide study of 6.4 million adults, which tried to correct for the "healthy vaccinee" effect (the fact that people who get vaccinated tend to be healthier to begin with), still found that all six vaccines reduced all-cause mortality during the epidemic period, with effectiveness ranging from about 49% for Pfizer to 75% for Janssen [18]. A 2025 Estonian study found that pre-infection vaccination reduced the risk of a heart attack or stroke in the year after infection by about 29% and cut all-cause mortality by 68% [17].

But these benefits are heavily concentrated in older, frailer people. A 2025 cost-effectiveness analysis in the US found that vaccinating people 65 and older was cost-saving, but for adults 18-49 it cost over $115,000 per quality-adjusted life year gained [37]. That is a fancy way of saying the benefit is small enough that you have to spend a lot to get it. The same study estimated that vaccinating 100,000 people aged 18-49 prevented about 39 hospitalizations and 1.4 deaths [37]. For people 65 and older, the same 100,000 vaccinations prevented 391 hospitalizations and 43 deaths [37].

The safety side matters most for young males. A living BMJ systematic review found that myocarditis after mRNA vaccines occurs at a rate of 50-139 cases per million doses in males aged 12-17, and 28-147 per million in males 18-29 [22]. Most cases are mild and resolve quickly, but the same review found that in the small number of patients followed for three months, over half still had persistent abnormalities on echocardiogram or ongoing symptoms [22]. The risk is higher with Moderna than Pfizer, and higher with shorter intervals between doses [22].

The evidence I was given does not include a single long-term safety trial that compared vaccinated people to a true unvaccinated control group and followed both for years. The most informative study design was never run. The safety data comes from passive surveillance systems that detect almost nothing by design, and from short-term follow-up. The benefit data comes mostly from observational studies during the first waves, when the virus was deadlier and the vaccines matched the circulating strain better than they do now.

My call: for people over 65 or with serious health conditions, the evidence shows a real benefit that clearly outweighs the known risks. For healthy young adults, especially males under 30, the benefit is small and the myocarditis risk is not zero. The evidence does not support a one-size-fits-all recommendation. Confidence: moderate.