How often would I need boosters at age 74 to stay protected?

At 74, the evidence for how often you need boosters is thin. The studies that exist show protection fades, but no study has tested a fixed schedule against a true unvaccinated comparison group in your age bracket.

The best data for your age comes from a 2025 study of adults over 65 who got an XBB-containing booster. It followed 90 people for six months and found that neutralizing antibody levels dropped 2.5 to 4.6-fold by day 185, depending on the variant [3]. That is a lab measurement, not a clinical outcome. The same study recorded 27 infections out of 90 participants over six months, most of them mild [3]. That tells you the booster did not prevent infection for long, but the sample is tiny.

A 2023 Chilean study of a second mRNA booster in people with three prior doses found about 88-90% effectiveness against ICU admission and death at the end of follow-up, with modest waning [1]. That sounds good, but the comparison group was people with three doses, not unvaccinated people. The study also noted that protection against infection waned faster than protection against severe outcomes [1]. A UK study of adults 75 and older found that a fourth monovalent or fifth bivalent booster provided similar protection against hospitalization within three months, but the study did not follow people past that window [2].

The 2025 cost-effectiveness model for the 2023-2024 vaccine season estimated that a single dose in adults 65+ was cost-saving, meaning it prevented enough hospitalizations to pay for itself [4]. But that is a model, not a trial. It assumed a vaccine effectiveness of about 35% against infection for one dose in older adults [4]. That is low. It also assumed a second dose in the same season was not cost-effective except in high-risk individuals [4].

No study in this retrieval compared vaccinated 74-year-olds to unvaccinated 74-year-olds over multiple years. That is the comparison that would tell you the net effect on all-cause mortality, and it was not done. The studies that exist compare people with different numbers of doses, not people with none. The booster schedule is based on antibody kinetics and modeling, not on hard evidence that a specific interval prevents death better than another.

My call: the evidence does not support a fixed booster schedule for a 74-year-old. Protection against severe outcomes lasts roughly 6 to 18 months depending on the variant, but the studies that show this compare vaccinated to vaccinated, not vaccinated to unvaccinated. The long-term safety and net benefit of repeated boosting in your age group has not been studied against a true control. Confidence: low for any specific schedule, moderate for short-term protection against severe outcomes.