A commentary on measles vaccine in the context of outbreaks: Viral evolution, waning immunity and public trust.

The measles vaccine, introduced over 60 y ago, has been proven to be both safe and effective. Despite the genetic diversity of the measles virus, eradication is considered possible with near-complete coverage of the two-dose vaccination schedule. However, real-world data show that this level of control has not yet been achieved. In addition to outbreaks among unvaccinated individuals, increasing numbers of measles cases are occurring among fully vaccinated, seropositive individuals. Both primary and secondary vaccine failures have been documented. Reduced vaccine effectiveness may occur in people with innate immune deficiencies, immunocompromised individuals (including those with HIV), and patients with chronic conditions such as diabetes. Furthermore, in regions without circulating wild-type virus, vaccine-induced antibody levels tend to decline over time and the impact of this may be more significant among infants. Emerging evidence highlights the importance of T lymphocyte - mediated immunity on effective B cell mediated immune response. Compounding the challenge, measles vaccination and infection are politicized, undermining public trust. Given the high transmissibility of measles, its potential for presymptomatic transmission, and the absence of specific early symptoms, complete eradication may not be feasible in the near term. Nevertheless, combining vaccine advocacy, transparent communication, and ongoing research will be critical to improving global vaccination strategies and public confidence.