Old age, unhealthy lifestyle weaken COVID-19 vaccine protection against severe illness

Vaccines provide the best defense against COVID-19, but they are not without limitations. Acute infections still occur in some, especially those who are older, smokers, obese, or with type 2 diabetes (T2D), as reported in a study.

“Our results suggest that the effectiveness of COVID-19 vaccines in preventing severe illness may be diminished by host characteristics, including age and conditions associated with unhealthy lifestyles (namely smoking, obesity, and T2D),” according to the investigators.

The analysis included 1,607 Mexican adults with confirmed COVID-19 despite having been immunized, with a total follow-up of 21,713 person-days. The overall risk of pneumonia was 1.98 per 1,000 person-days (43 per 21,713), and the mortality in this group was 53.5 percent (23/43). Patients with vs without COVID-19 pneumonia were older (mean 65.5 vs 49.5 years; p<0.001) and had a higher prevalence of chronic noncommunicable conditions.

In multivariable generalized linear regression models, the risk of developing COVID-19 pneumonia was elevated among vaccinated individuals aged ≥65 years (risk ratio [RR], 1.04, 95 percent confidence interval [CI], 1.02–1.07), smokers (RR, 1.07, 95 percent CI, 1.04–1.10), adults with obesity (RR, 1.02, 95 percent CI, 1.01–1.04), and those with T2D (RR, 1.03, 95 percent CI, 1.01–1.05).

With increasing age, older people are at risk of a progressive decline in function of the immune system, called immunosenescence, which could be related to diminished humoral and cellular immune responses, the investigators said.

Meanwhile, smoking, obesity, and T2D have been associated with poor disease outcomes among unvaccinated individuals, they added.