Are measles, mumps and diphtheria outbreaks harbingers of worse to come?

8 Jun 2023

So far this year the National Institute for Communicable Diseases has issued reports on three different outbreaks of vaccine-preventable diseases – measles, mumps and diphtheria. Elri Voigt spoke to local experts about what this tells us about the country’s immunisation programme and the potential for future outbreaks.

The measles, mumps and diphtheria outbreaks were not unexpected. As previously reported, experts have been warning about the potential for an outbreak of vaccine-preventable diseases among children due to declining immunisation rates during the Covid-19 pandemic, which came on top of immunisation coverage rates that weren’t great to begin with.

Dr Kerrigan McCarthy, a pathologist at the Centre for Vaccines and Immunology at the National Institute for Communicable Diseases (NICD), tells Spotlight that vaccination coverage rates in the country are still less than optimal for most vaccines.

“The primary reason for our measles outbreak was low vaccination coverage. In order to prevent outbreaks, over 95% of persons in the population need to be immune, so vaccination coverage rates must be high,” she says. “Other vaccine-preventable diseases also require high population immunity levels and, therefore, high vaccination coverage rates, ranging from 75% (rubella) to 90% (pertussis). Suboptimal vaccination coverage,” McCarthy says, “means that when cases of disease occur, circulation of these bacteria or viruses is possible within the community. Sporadic cases may develop into cluster outbreaks and when large numbers of susceptible persons are present, community transmission and full-scale outbreaks may happen.”

The three outbreaks

The current measles outbreak started late in 2022 (Spotlight reported on it here). On 2 June 2023, the total number of measles cases detected was 1,034 across the eight provinces with outbreaks.

On 19 May, the NICD issued an alert for healthcare workers that two cases of diphtheria had been detected in April and, on 26 May, a mumps outbreak was confirmed as the NICD had identified 580 positive cases so far this year.

McCarthy says the last major measles outbreak was in 2009-2010. For diphtheria, only seven cases were detected in the country in the 15 years from 2000 to 2015. In 2017, there was an outbreak of 15 cases in KwaZulu-Natal and six in the Western Cape.

She adds that occasional mumps outbreaks are to be expected, since the mumps vaccine is not part of the Expanded Programme of Immunisation (EPI) in the public health sector. “Mumps outbreaks tend to occur every four to six years in the absence of the vaccine in the routine expanded programme of immunisation.”

‘Unusual, but not unheard of’

Dr Anthonet Koen, a senior researcher at the Vaccines and Infectious Diseases Analytics research unit at the University of the Witwatersrand, tells Spotlight that cluster outbreaks of measles occur frequently in the country. She suggests the diphtheria outbreak is more unexpected.

“The last reported diphtheria outbreak was in 2017, according to NICD stats, so I would not say we can consider it normal. What we are likely seeing is a consequence of the Covid-19 pandemic where limited access to primary healthcare facilities has left children unvaccinated and now vulnerable to these types of preventable diseases. But it can also just be coincidence,” she says.

Professor Susan Goldstein, deputy director and COO of PRICELESS, the South African Medical Research Council’s Centre for Health Economics and Decision Science, tells Spotlight that even before the pandemic vaccination rates were not what they should be, but that the pandemic has made matters worse in more ways than one.

“It’s very worrying [the three outbreaks]… these are life-threatening diseases, especially for under-five [year-olds]. It can spread into older age groups, but generally, we’re talking about children under five,” she says. “And we just can’t afford that on top of Covid. What happened during Covid was that there was an increase in malnutrition because of the huge financial problems, etc, that makes all these illnesses more severe and more life-threatening.”

“It is a little bit unusual to have so many of them at once,” says Dr Gary Reubenson, an infectious disease paediatrician working with the Rahima Moosa Mother and Child Hospital in Johannesburg, which is affiliated to Wits, in reference to the three outbreaks. “But it’s not unheard of,” he says, “Those three in particular – measles, mumps and diphtheria – have similar routes of transmission. They all spread predominantly person to person through the respiratory route. If they are going to happen at the same time, it’s not impossible that they’re going to occur together.”

Diphtheria and measles of more concern than mumps

Out of the three outbreaks, measles and diphtheria are more concerning than mumps because of the severity of illness.

Reubenson explains that mumps is typically less serious than some other vaccine-preventable childhood diseases. “Most people who experience it will feel unwell for a few days, but it very seldom causes any serious harm,” he says.

The diphtheria outbreak, on the other hand, is a greater cause for concern.

McCarthy says the disease can lead to a number of “life-threatening complications, including respiratory obstruction, myocarditis and peripheral neuropathy”.

“Because diphtheria is preventable by vaccination and persons who have completed their primary vaccination series and are up to date with their boosters, only unvaccinated persons are at risk of diphtheria,” she says.

“Diphtheria is a potentially serious illness that can cause deaths in children and young adults. It has the potential to spread quite rapidly in settings where there are suboptimal vaccination rates,” says Reubenson. “At the moment, there are relatively few cases, but it is an area of some concern and something that we, as healthcare workers, need to be aware of so that potential cases can be investigated and managed appropriately.”

Read more in Daily Maverick: As schools open, there is the potential for the measles outbreaks to get worse

Regarding the measles outbreak, Reubenson says surveillance data from the NICD suggest that the outbreak may have reached its peak and has started declining. However, he cautions healthcare workers to remain vigilant.

“Part of the reason that the measles outbreak is potentially tailing off could be the additional vaccines that were offered to children during the recent catch-up campaign, in addition to all the other measures that have been put in place,” he says.

He adds that at the moment, a catch-up immunisation drive is not necessary to curb the diphtheria or mumps outbreaks.

Coverage concerns

Spotlight requested the latest childhood immunisation figures following the recent immunisation catch-up drive. The request was acknowledged by the National Department of Health, but no response had been received by the time of publication.

Data from the 2019 EPI National Coverage Survey showed suboptimal coverage in most districts before the pandemic. The national target is to have 90% of children fully vaccinated under one year of age.

As Spotlight previously reported, nationally only about 77% (76.8%) of children surveyed had received all 14 age-appropriate vaccines from birth to 18 months. The Northern Cape had the highest coverage (81.6%), followed by Gauteng (81.4%). Limpopo had the lowest coverage at 70.5%.

Coverage varied widely by district, ranging from 53% to 100% between the 52 districts. Only seven managed to achieve the national target for children under one.

I think we’ve been maybe lucky until now, but with these added problems of load shedding and poor water supply and poverty, we may not be so lucky.

Whether we have returned to those pre-Covid levels is unclear, but in 2022 Dr Haroon Saloojee, professor in the Division of Community Paediatrics at Wits and a member of the ministerial National Advisory Group on Immunisation (NAGI), stated that we may have returned to the same level of vaccine coverage as before the pandemic based on data he has seen at NAGI.

But this doesn’t mean we aren’t still seeing the effects of lower rates in 2020 and 2021. In fact, according to Reubenson, the drop in routine immunisation rates during the Covid-19 pandemic may partly explain why the diphtheria and measles outbreaks are occurring at the same time.

He adds that improvement in the country’s surveillance system for communicable diseases that took place due to the Covid-19 pandemic may have also allowed for the detection of these outbreaks more rapidly than in the past.

Other potential outbreaks

Spotlight asked the experts about a potential resurgence in vaccine-preventable diseases based on the recent outbreaks. They agreed that at this point there isn’t necessarily going to be a dramatic resurgence of other vaccine-preventable diseases, but that low vaccination coverage does pose a risk for potential outbreaks of other diseases and coverage should be improved urgently.

Reubenson says he doesn’t foresee any dramatic outbreaks of other vaccine-preventable diseases at this point, however improving immunisation coverage is essential, and predicting outbreaks is imprecise and difficult.

Read Daily Maverick’s cholera coverage here

“The important point is that we need to maintain and improve those vaccination rates to protect the individuals who are being vaccinated and also at a population level to ensure that if one of these pathogens were introduced that the chances of it spreading, causing outbreaks and potentially deaths can be kept as low as possible,” he says.

Goldstein says she is hopeful that the country is not about to see a resurgence of vaccine-preventable diseases but adds that if a disease is introduced into an area where there are low vaccination rates, there could be a resurgence.

“It’s a bit of a luck-of-the-draw kind of thing, but the potential is definitely there because of the poor [immunisation] rates and it has been there for a number of years. I think we’ve been maybe lucky until now, but with these added problems of load shedding and poor water supply and poverty, we may not be so lucky,” she says.

For Koen, the outbreaks do not signal a need to panic just yet.

“Having cluster outbreaks is not entirely uncommon, so I wouldn’t think we need to panic, but we definitely need to ensure that we have adequate primary healthcare facilities that are adequately stocked with the required vaccines as well as sufficient and knowledgeable staff,” she says.

McCarthy is, however, less optimistic.

“There is a high risk of outbreaks of key vaccine-preventable diseases including polio [and] rubella,” she says. “Low vaccination coverage rates for other conditions will imply a greater risk to unvaccinated, susceptible persons, and to our communities should the disease condition be imported.”

She adds that low vaccination coverage of other diseases is likely to be contributing to an “increased impact of childhood tuberculosis (preventable by BCG vaccination), tetanus (preventable by tetanus toxoid), pertussis (whooping cough), hepatitis B, Haemophilus influenza type B, and HPV infection (increasing the risk for cervical cancer) on our population.”

The potential outbreaks McCarthy is most concerned about are polio and rubella. Polio is included in the public health sector routine immunisation schedule, rubella is not.

If we stop vaccinating against these preventable diseases, then we are creating an extremely vulnerable future generation of individuals.

“Perhaps most concerning is the risk of polio importation into South Africa, as both polio vaccination rates and detection of cases of acute flaccid paralysis (the clinical syndrome with which polio presents) are suboptimal,” she says. “Furthermore, cases of wild polio type 1 were detected in northern Mozambique in 2021/2 and environmental strains of a neurovirulent polio virus have been detected in Botswana in 2022. Large movements of persons between our countries occur due to travel and trade and it is highly likely that these dangerous viruses may be imported. Hence, it is imperative that our vaccination coverage be strengthened.”

Koen adds to the list.

“We definitely need to be on high alert for any signs of the other vaccine-preventable diseases that are currently in our vaccination schedule,” she says. These include pneumococcal conjugate disease, which occurs despite having a vaccine because there are so many variants.

According to Koen, the current vaccine protects against the 13 most common variants, as well as hepatitis and rotavirus. She adds that the current pneumococcal vaccine will soon be replaced by one that only protects against 10 variants.

Improving immunisation rates

Reubenson stresses that the vaccines given to children as part of their routine immunisation schedule are safe and effective. “The vaccines that are currently being provided have been incredibly well studied. They are among the safest interventions available to modern medicine. And they work. Well-conducted scientific studies have proven that they work.”

He adds: “We [as healthcare providers] need to be aware of the conditions and make parents and their children aware so that they access vaccines, make sure that the vaccines are available at vaccination sites whenever they’re needed, [and] make sure that when people present to those sites that the healthcare workers provide the vaccines and don’t defer them. It is important to not miss those opportunities when they do present.”

Goldstein says communication and leadership from the Department of Health, as well as among healthcare workers, is needed.

“For me, it’s really about making sure that we have consistent communication through community health workers about the importance of immunisation and making sure that kids get their immunisation and [are] up to date,” she says. “For me, it’s about leadership. I think health workers know that they must give immunisations. But it’s really about motivating, encouraging, telling people the benefits, [and] how many millions of lives are saved every year through this procedure.”

Koen explains what would happen if we were to stop vaccinating:

“If we stop vaccinating against these preventable diseases, then we are creating an extremely vulnerable future generation of individuals and we will then very likely see resurgences of all of these really horrible diseases at an even higher rate. It will place a lot of stress on our already stressed healthcare system.” DM

This article was published by Spotlight – health journalism in the public interest.

Spotlight logo

Categories:

Tags:

DM is much better if you are signed in...

South Africa