Whooping cough epidemic in SA throws up shockingly low vaccination rates
Poor vaccine coverage is one of the causes of the spike, says an expert, as crisis reveals unsettling stats for other diseases as well
There is an outbreak of highly infectious whooping cough in SA, despite it being a vaccine-preventable disease. The National Institute for Communicable Diseases (NICD) has declared a whooping cough epidemic in the Nelson Mandela Bay health district in the Eastern Cape. It detected 116 cases in the Port Elizabeth region in the first two months of 2019.
Babies are most at risk of infection and death because they cannot be vaccinated against whooping cough before they are three months old.
The NICD told Times Select it also looks for pneumonia and flu-like outbreaks in five provinces, and in 2018 reported a spike in whooping cough in all of them: Mpumalanga, Gauteng, KwaZulu-Natal, the Western Cape and North West.
A vaccine for whooping cough disease, or pertussis, is given at six, 10 and 14 weeks of age, with a booster offered at 18 months.
Scientists say low vaccination rates may be one reason for the spike in cases.
A world-renowned vaccine expert and professor of vaccinology at Wits University, Shabir Madhi, said the outbreak resulted from “a combination of factors, among which is poor vaccine coverage”.
“There has also been an increase in pertussis in infants younger than three months who are too young to be protected by immunisation and develop the most severe disease.”
Because babies are the most vulnerable, health authorities have been vaccinating pregnant mothers in Port Elizabeth and surrounds to protect their unborn children, according to the NICD. At least three babies are confirmed to have died from pertussis in 2018, the institute reported in a diseases communique.
But the estimates of cases and deaths are always lower than thought, according to the head of the NICD’s Centre for Respiratory Disease and Meningitis, Associate Professor Cheryl Cohen.
“The number of notified cases is always a minimum estimate of the number of cases of disease, because of various factors such as persons not seeking healthcare and the healthcare worker not considering the diagnosis or the case not being notified [reported]”.
Cohen said the NICD was investigating whether the children who had contracted pertussis in the Eastern Cape had been vaccinated.
“The NICD is working with local public health authorities in the relevant districts to collect vaccination history from the pertussis cases involved in the Eastern Cape outbreak.”
Estimates had shown the pertussus vaccine rate was too low.
“In 2016, Statistics South Africa estimated the coverage of the pertussis-containing vaccine to be 65% for the third dose of the vaccine, which is below the World Health Organisation’s (WHO) recommended target of >90% coverage. It is possible that insufficient vaccination ... has contributed to the increase in cases.”
However, SA authorities don’t know what percentage of children are vaccinated against diseases including whooping cough, measles, polio and tetanus.
“We don’t have really good data on vaccine coverage. It’s wobbly,” said pharmacologist Andy Gray from the University of KwaZulu-Natal. He said there were questions about the accuracy of health records and disputes about how to calculate the vaccine rate.
Madhi said the WHO estimated that in SA about 75% of toddlers received the pertussis vaccine and about 73% of children were vaccinated against measles, one of the most infectious diseases in the world.
“This is much lower than national department of health estimates of about 90%.”
He said there were limitations in both the department of health and WHO estimates and a proper nationwide census to determine vaccine coverage was needed. Two weeks ago, the health minister Aaron Motsoaledi launched a vaccine census.
Madhi said: “The vaccine coverage survey will for the first time since 1997 provide us with reliable data on vaccine coverage in SA, although it is mainly focused on vaccines given during the first two years of life.”
Gray said the survey was extremely important. He said authorities needed to know whether middle-class people were vaccinating their children in light of the fact that middle-class people overseas were “vaccine hesitant”.
Middle-class people and those in gated communities did not let government or census workers into their homes, which could pose a problem, he added.
With whooping cough, the epidemic is not just caused by low vaccination rates, but by the type of vaccine in use.
Whooping cough is one the most difficult vaccine-preventable diseases to control, said Madhi. The newer vaccine, which is popular because it has fewer side-effects, required a booster dose at schoolgoing age and in adolescence, unlike other vaccines. Many countries did not offer this. SA clinics did not offer the booster dose for older children but this was “under consideration”.
Cohen urged parents to vaccinate their children.
“Vaccination remains the most effective method of protecting children against diseases such as pertussis.”