PAHO urges countries to strengthen vaccination efforts as diphtheria cases rise in the Americas

Washington, D.C., 15 June 2026 (PAHO) - The Pan American Health Organization (PAHO) is calling on countries in the Americas to strengthen routine immunization programs and close vaccination gaps following an increase in diphtheria cases reported in the Region.

According to a new Epidemiological Alert issued by PAHO, 163 confirmed cases of diphtheria, including five deaths, were reported in the Americas in the first 21 weeks of 2026, more than double the number reported in 2025 and significantly above the average recorded in recent years. The cases were reported in Brazil, Haiti, and Peru, with Haiti accounting for the vast majority of infections (159 cases) and all deaths.

More than half of confirmed cases this year occurred among people who were unvaccinated or had unknown vaccination status.

The increase comes as vaccination coverage against diphtheria remains below the levels needed to prevent outbreaks. In 2024, regional coverage for the third dose of the diphtheria, tetanus and pertussis (DTP3) vaccine declined to 87%, well below the 95% target recommended to provide community protection. Several countries continue to report coverage levels below 80%, while others have high dropout rates between the first and third vaccine doses.

In its alert, PAHO warns that, given the current situation, in which diphtheria vaccination coverage has remained below optimal levels in recent years, as well as the emergence of new cases in some countries of the Region, countries should close vaccination gaps by reinforcing routine immunization programs, catch-up vaccination, and follow-up activities. PAHO also urges countries to strengthen epidemiological surveillance of vaccine-preventable diseases.

The decline in vaccination coverage has left pockets of the population vulnerable to vaccine-preventable diseases. While the Americas have made significant progress in controlling diphtheria over recent decades, the disease continues to circulate globally and can re-emerge when vaccination coverage falls.

PAHO urges countries to use microplanning strategies to identify and vaccinate populations that have been missed. The Organization also recommends taking advantage of every contact with the health system to verify vaccination status and complete immunization schedules.

The alert notes that "it is urgent to increase coverage of both the primary series (3 doses) and the recommended boosters (3 doses) among children, adolescents, and adults" to prevent new cases and outbreaks.

In addition to vaccination, PAHO is calling on countries to strengthen surveillance, ensure rapid laboratory confirmation of suspected cases, maintain adequate supplies of diphtheria antitoxin, and train health workers in outbreak detection and response.

Diphtheria is a serious bacterial infection caused by Corynebacterium diphtheriae and transmitted through respiratory droplets. It is characterized by the formation of a thick gray membrane (pseudomembrane) in the throat and tonsils, which can obstruct the airway. If left untreated, toxins produced by the bacteria can lead to severe breathing difficulties, as well as damage to the heart and nervous system, and can be fatal. Unvaccinated or under-vaccinated individuals remain at highest risk of infection.

PAHO recommends that countries provide children with the highest level of protection by achieving and maintaining vaccination coverage of at least 95% with the primary three-dose DTP series and the recommended booster doses. The Organization also advises countries to strengthen public awareness of diphtheria symptoms and the importance of vaccination, while ensuring health workers are equipped to rapidly detect, report, and manage suspected cases.

"Vaccination is key to preventing cases and outbreaks," PAHO states in the alert, emphasizing that closing vaccination gaps and sustaining high coverage levels remain essential to protecting populations across the Americas.