Measles susceptibility and risk of viral reintroduction in a large urban center in northeastern Brazil
1
Institute of Collective Health, Federal University of Bahia, Bahia, Brazil
2
René Rachou Institute, Oswaldo Cruz Foundation, Minas Gerais, Brazil
Popul. Med. 2026;8(Supplement Supplement 1):
ABSTRACT
INTRODUCTION:
This study aimed to analyze changes in the age distribution of protective measles antibodies in the population of Salvador, Brazil, in 2000 and 2024.
METHODS:
A seroprevalence study of measles IgG antibodies was conducted among 1,508 individuals residing in 37 areas of Salvador, Bahia, Brazil, previously investigated in a similar survey in 2000. Data were collected through household interviews using a structured questionnaire addressing sociodemographic characteristics, vaccination history, and previous measles infection. Venous blood samples were obtained for IgG antibody titration. Mean IgG prevalence was calculated according to age group, living conditions, and other variables. The association between antibody titers, vaccination status, and history of measles infection was assessed using logistic regression.
RESULTS:
The sample consisted predominantly of women (61.5%), with a mean age of 42 years. Overall, 35% had completed secondary education or had incomplete higher education, 39% reported a family income of one to two minimum wages, 29.4% reported previous measles infection, and 77.3% had been vaccinated, with lack of awareness about the need for vaccination being the main reason for non-vaccination. ELISA seropositivity was 82.4%, with antibody concentrations predominantly ranging from 275 to 1,000 IU/L; among seropositive individuals, 49.2% denied prior measles infection. The highest seroprevalence was observed among individuals older than 50 years (92.1%), whereas the highest proportion of seronegative individuals occurred in the 20–29-year age group (39.6%), which showed a marked decline in seropositivity between 2000 and 2024 (from 95.7% to 60.4%). Age was a significant predictor of seropositivity (p = 0.01).
CONCLUSIONS:
A seroprevalence of 82.4% is insufficient to ensure herd immunity in the event of viral circulation. This finding is particularly concerning when compared with the first survey conducted in Salvador in 2000, in which seropositivity reached 95.1%.
This study aimed to analyze changes in the age distribution of protective measles antibodies in the population of Salvador, Brazil, in 2000 and 2024.
METHODS:
A seroprevalence study of measles IgG antibodies was conducted among 1,508 individuals residing in 37 areas of Salvador, Bahia, Brazil, previously investigated in a similar survey in 2000. Data were collected through household interviews using a structured questionnaire addressing sociodemographic characteristics, vaccination history, and previous measles infection. Venous blood samples were obtained for IgG antibody titration. Mean IgG prevalence was calculated according to age group, living conditions, and other variables. The association between antibody titers, vaccination status, and history of measles infection was assessed using logistic regression.
RESULTS:
The sample consisted predominantly of women (61.5%), with a mean age of 42 years. Overall, 35% had completed secondary education or had incomplete higher education, 39% reported a family income of one to two minimum wages, 29.4% reported previous measles infection, and 77.3% had been vaccinated, with lack of awareness about the need for vaccination being the main reason for non-vaccination. ELISA seropositivity was 82.4%, with antibody concentrations predominantly ranging from 275 to 1,000 IU/L; among seropositive individuals, 49.2% denied prior measles infection. The highest seroprevalence was observed among individuals older than 50 years (92.1%), whereas the highest proportion of seronegative individuals occurred in the 20–29-year age group (39.6%), which showed a marked decline in seropositivity between 2000 and 2024 (from 95.7% to 60.4%). Age was a significant predictor of seropositivity (p = 0.01).
CONCLUSIONS:
A seroprevalence of 82.4% is insufficient to ensure herd immunity in the event of viral circulation. This finding is particularly concerning when compared with the first survey conducted in Salvador in 2000, in which seropositivity reached 95.1%.
| eISSN: | 2654-1459 |
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