Rubella seroprevalence among mothers and incidence of congenital rubella three years after rubella vaccine introduction in Vietnam

ABSTRACT

Following a rubella outbreak in 2011, Vietnam implemented a mass measles-rubella vaccination campaign for children aged 1–14 years in 2014–2015, further expanding the target age to 16–17 years in 2016; routine vaccination was introduced in 2014. However, there was concern that a substantial proportion of women of child-bearing age were still susceptible to rubella, with the fear of congenital rubella emergence. Thus, we conducted a prospective cohort study in Nha Trang, Vietnam, from 2017–2018 to investigate pregnant women’s susceptibility to rubella infection, the incidence of congenital rubella infection, and factors associated with susceptibility. Cord blood was tested for rubella-specific immunoglobulin M (IgM) and IgG; neonatal saliva and cord blood specimens were examined for rubella-RNA. We analyzed 2013 mother-baby pairs. No baby was rubella-IgM or rubella-RNA positive. Overall, 20.4% of mothers were seronegative (95% confidence interval, 18.6%–22.1%). The seronegativity was significantly low among mothers aged <35 years. We found that maternal age groups of 20–24 and 25–29 years, and the lack of self-reported vaccination history were significantly associated with seronegativity. Many pregnant women who were not covered by the vaccination campaign are still at risk of rubella infection.

KEYWORDS:

• Rubella-containing vaccine
• Vietnam
• infants
• pregnant women
• seronegative
• seroprevalence
• congenital rubella syndrome

Acknowledgments

We would like to thank the participants and the staff in Vietnam who cooperated in the study. We are also grateful to Dr. Kiyoko Okamoto and Dr. Makoto Takeda (Department of Virology III, National Institute of Infectious Diseases, Tokyo, Japan) who provided rubella virus RNA as control, Ms. Taeko Akase (Department of Pediatrics, Nagasaki University Hospital, Nagasaki, Japan) who supported checking the samples and extracting the virus RNA, and Editage [http://www.editage.com] for providing English language editing service.

Disclosure of potential conflicts of interest

No potential conflicts of interest were disclosed.

Additional information

Funding

This research was supported by Grants-in-Aid for Scientific Research from Japan Society for the Promotion of Science [KAKENHI, 16H05846], the Japan Initiative for Global Research Network on Infectious Diseases (J-GRID) from Ministry of Education, Culture, Sport, Science & Technology in Japan, and Japan Agency for Medical Research and Development (AMED) [JP20wm0125006].