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Published on: May 13, 2020
Outbreak of measles among persons with secondary vaccine failure, China, 2018
Zhujiazi Zhang1, Meng Chen1, Rui Ma1
1Department of Immunization and Prevention, Beijing Center for Disease Control and Prevention, Beijing Research Center for Preventive Medicine, Beijing, China.
Abstract:
Although the incidence of measles has been dramatically reduced by the highly effective measles vaccine, cases of measles and outbreaks continue to occur in vaccinated population because of immunization failure. We report on an outbreak in which two cases had previous evidence of measles immunity and then one of them transmitted measles infection to an unvaccinated contact. The cases and contacts exposed during the outbreak were investigated. Clinical information and epidemiological information were obtained. Serum samples were collected for measles-specific immunoglobulin M (IgM), immunoglobulin G (IgG) and IgG avidity. Throat swabs were obtained to test for measles virus RNA. Two measles cases (case 1 and case 2) who have received one dose of MCV in past 5 years, and both working at a hospital in Beijing, occurred in 18th and 20nd of January, respectively. Out of the 102 contacts, one additional case (case 3) who had a close, long-term co-exposure with case 1 was reported subsequently. No additional cases of measles occurred among 15 contacts of case 3. The index case was not ascertained through the outbreak review. All three cases had laboratory confirmation of measles infection. Both case 1 and case 2 had high-avidity IgG antibody characteristic of a secondary immune response and developed a modified clinical presentation. This report confirms that a vaccinated individual with documented secondary vaccine failure (SVF) could transmit measles and is the second report since a New York City outbreak (the first report in China). The outbreak represented a series of rare events, so we can conclude that the SVF individuals in the transmission chain of measles are unlikely to threaten measles elimination. The importance of the herd immunity in preventing transmission and sensitive surveillance activities in case of misdiagnosis is emphasized.
Insights
Vaccinated individuals can transmit measles due to secondary vaccine failure (SVF). However, these rare transmission events are unlikely to hinder measles elimination efforts, highlighting the importance of herd immunity.
Area of Science:
- * Infectious Diseases
- * Vaccinology
- * Epidemiology
Background:
- * Measles incidence is significantly reduced by vaccination, but outbreaks still occur in vaccinated populations due to immunization failure.
- * Secondary vaccine failure (SVF) can occur, where vaccinated individuals lose immunity over time.
- * Documented transmission from a vaccinated individual with SVF is rare but important to understand for public health.
Purpose of the Study:
- * To investigate a measles outbreak involving vaccinated individuals in Beijing.
- * To confirm transmission from a vaccinated case with documented secondary vaccine failure.
- * To assess the risk of measles transmission from SVF individuals and its impact on elimination goals.
Main Methods:
- * Retrospective investigation of measles cases and contacts exposed during an outbreak.
- * Collection of clinical and epidemiological data.
- * Laboratory confirmation including measles-specific IgM, IgG, IgG avidity, and viral RNA detection.
Main Results:
- * Three laboratory-confirmed measles cases occurred, two of whom were vaccinated with one dose of measles-containing vaccine (MCV) within 5 years.
- * Both vaccinated cases exhibited high-avidity IgG antibodies, indicative of a secondary immune response, and modified clinical presentations.
- * One vaccinated case with SVF transmitted measles to an unvaccinated close contact; no further transmission occurred from this contact.
Conclusions:
- * Vaccinated individuals with documented secondary vaccine failure can transmit measles, as demonstrated in this Beijing outbreak.
- * The transmission events from SVF individuals appear to be rare and unlikely to jeopardize overall measles elimination.
- * Herd immunity remains crucial for preventing widespread transmission, and sensitive surveillance is vital for early detection and management of misdiagnosed cases.
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