‘Immunity gap’ drives rubella outbreak in South Africa

The National Institute for Communicable Diseases (NICD) has seen an increase in rubella cases across South Africa, with more than 8 000 positive cases identified at the end of September.

In 2024, health authorities reported more cases than in the entire fever-rash surveillance period since 2015. Rubella is also known as German measles.

More than 8 700 positive cases were identified up until the end of September, with 98% of cases occurring in children under 15 years of age, according to the NICD. The majority of children affected fell within the five-to-nine age group.

Rubella cases increase in 2024

“Whilst a seasonal increase in rubella cases is expected every year, usually occurring from September to December each year, the number of cases is much larger in 2024 compared with previous years,” the NICD said in a statement.

Medical experts attribute the surge in cases to children entering 2024 without prior rubella exposure or vaccination.

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Three key factors contributed to the large number of children lacking immunity in 2024:

• Rubella immunity or infection immunity lasts a lifetime. If children are not vaccinated or exposed to the virus naturally, they will continue to be at risk for contracting it.
• Before 2024, the rubella vaccine was not a regular component of South Africa’s Expanded Programme on Immunisation (EPI).
• The department/NICD fever-rash surveillance showed nearly no instances of rubella throughout 2020–2022, thanks to non-pharmaceutical actions used during the Covid-19 pandemic to stop the disease from spreading.

This means that children born between 2019 and 2021, and those aged five to 14 who hadn’t been infected before 2020, missed natural exposure to the wild-type rubella virus and vaccination.

‘Immunity gap’

“This has created an ‘immunity gap’ — i.e., a larger than usual number of children who are susceptible to rubella,” the NICD said. 

“The seasonal increase in 2024 has exposed these many susceptible children to infection, and thus, there are a larger number of rubella cases than in prior years.”

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The NICD said rubella is a self-limiting infection that presents with fever and a maculopapular rash, myalgia, enlarged lymph nodes, headache, and conjunctivitis.

Risk to pregnant women

Occasionally, persons may develop joint pain, low platelets, and mild encephalitis. The complications are usually self-limited.

“Rubella is of concern because of the risk of rubella infection in women of child-bearing age during the first trimester of pregnancy,” the NICD said.

“However, rubella infection carries a risk of congenital rubella syndrome. Women who are pregnant in their first trimester and acquire rubella may pass the infection onto their foetus, who may develop congenital rubella syndrome (CRS).”