What about the Moderna Covid vaccine? Should I keep getting boosters

The evidence for ongoing Moderna boosters is thin on hard outcomes and does not show a clear net benefit for most people.

The only retrieved study that directly tested Moderna booster safety found that the risk of myocarditis or pericarditis hospital admission in 16-39 year olds was elevated about 6-fold in the week after a Moderna booster, compared to baseline [4]. This was lower than the 56-fold spike seen after the second primary dose, but it was still a real, measurable risk [4]. A separate VAERS analysis claimed booster myocarditis rates were lower than primary series rates, but VAERS is a passive reporting system that captures only a fraction of events by design [5]. That study cannot prove safety; it can only show that fewer people bothered to report.

On the benefit side, the evidence is from the Omicron era and shows that a booster restores some protection against symptomatic infection, to about 60-72%, but that is still lower than the roughly 90% protection boosters gave against the Delta variant [1]. A 2025 Egyptian cohort study of healthcare workers found that vaccination alone (including boosters) showed no statistically significant protection against infection once adjusted for confounders; only hybrid immunity from prior infection plus vaccination showed a clear benefit [2]. The Moderna primary series was 94% effective in its original placebo-controlled trial, but that trial was run before Omicron existed and before repeated boosting was a question [3].

The key question the evidence does not answer: whether repeated boosting produces diminishing returns or net harm over several years. The retrieved studies cover at most a few months after each dose. No long-term trial compares people who get annual boosters to people who stop after the primary series. The mechanism of immune imprinting—where the immune system becomes locked into responding to the original spike strain and struggles to handle new variants—is a documented concern that these studies do not address.

My call: the evidence does not support routine annual Moderna boosters for a healthy person who has already had the primary series and a prior infection. The myocarditis risk, though lower than with the second dose, is still measurable, and the benefit against infection is modest and short-lived. Confidence: moderate, because the evidence base is narrow and lacks long-term comparative trials.