Tragedy struck South Sudan earlier this month when a measles vaccination campaign went wrong, and 15 children died.
The 15 children, all under the age of 5, died of severe sepsis and toxicity due to contaminated measles vaccine, according to a statement by the WHO. According to the investigation, conducted by the National Adverse Events Following Immunization (AEFI) Committee and supported by WHO and UNICEF, the team conducing the vaccination event was not properly trained and did not adhere to WHO-approved immunization safety standards. These standards are pretty straight-forward and are what you’d expect international immunization standards to be, such as following the vaccine manufacturers guidelines, having enough syringes, maintaining the cold-chain, safely disposing of the bio-hazardous material, etc. So where did the campaign in South Sudan go wrong?
Well, it went wrong in a couple different ways. First, measles (MMR) vaccine needs to be reconstituted. This means it comes as a dry powder in a vial and that vial comes with another vial of liquid. The liquid needs to be added with a syringe to the powder vial and the powder reconstituted (essentially dissolved) before the vaccine can be administered. The South Sudan team used the same reconstitution syringe for multiple vials, when you should use one per vial, so when the syringe became contaminated during the day that contaminated syringe was then contaminating the subsequent vials of vaccine. And that contaminated vaccine was being given to the children.
Second, measles (MMR) vaccine requires refrigeration. Even though the vaccine itself is lyophilized (powder), the diluent (liquid it gets mixed with) needs to be refrigerated. That didn’t happen in this instance. The vaccine and diluent were stored in a building with no refrigeration for four days before the vaccination event.
At this event a total of 300 children were vaccinated during the campaign and thirty-two children additional suffered symptoms of sepsis and toxicity but survived.
Now I know that the re-use of the reconstitution syringe could have been a training issue, a lack of adequate supplies, etc. and those issues might be easily remedied in the future. But for the broken cold-chain, the solution is probably not as simple as finding a refrigerator. In some rural areas refrigeration is not always possible or reliable due to inconsistent electricity supplies. So this tragedy brings me to a question which I have a longstanding interest in – how can we (science) eliminate the need for a cold-chain or at the very least, reduce the burden of the cold-chain so vaccines can more reliably get to the people who need them?
Maintaining cold-chain in low-resource settings is particularly challenging. A lack of reliable electricity, poorly maintained equipment, and long distances between health facilities mean that vaccines can be exposed to improper temperatures which negatively affects their potency. Improving cold-chain technology is definitely an area for improvement for vaccine administration campaigns. PATH is one company working with partners on a few methods of cold-chain improvement, such as solar-powered refrigerators, modifications to food-grade refrigerators to make them meet WHO pharmaceutical-grade standards, developing better cooling materials for transport and better temperature monitoring so it’s easier to see when vaccines have gotten too hot or too cold and shouldn’t be used. We should also mention that vaccine makers may have the ability to make more thermostable vaccines. And while this may make the vaccines more expensive, a study of vaccine supply chain staff in low and middle-income countries indicates they would be willing to pay a little more for thermostable (more specifically heat-stable) vaccines and that those vaccines would provide flexibility in reaching remote areas.
South Sudan is facing many challenges to its healthcare system, because the instability and insecurity of many regions make getting healthcare to some residents very challenging. While this measles vaccination campaign tragedy has multiple causes, it does highlight the need for better investment in vaccine development to overcome the cold-chain requirement. This tragedy is a sad reminder of what’s at stake if science doesn’t do better.