With measles cases continuing to increase worldwide – despite it being 60 years since the first vaccine against the disease was licensed for public use – a glimmer of hope is on the horizon in the shape of injection-free immunisation.
In November, US-based Micron Biomedical received a $23.6m grant from the Bill & Melinda Gates Foundation to fund mass production of the company’s needle-free MR vaccines for low- and middle-income countries.
The vaccine is based on Micron’s microarray technology, which minimises or eliminates the need for cold chain storage, the company said. Patients or their caregivers can apply the virtually pain-free microarray to the skin and then press a button on it to deliver the vaccine.
Cases still rising
In 2022, more than 9m cases of measles were reported worldwide, and nearly 140 000 people, mostly children, died from the highly contagious disease.
The US Centres for Disease Control and Prevention (CDC) and the World Health Organisation (WHO), which recently released a report on the disease, called the statistics very concerning.
According to the CDC, children under five, adults over 20, pregnant women, and people with compromised immune systems have the highest risk of measles complications, which can include encephalitis and pneumonia, the latter being the most common cause of death from measles in children.
In the US, about one in five people with measles who are unvaccinated require hospitalisation.
Much progress toward eliminating infections had been made between 2000 and 2019, when the proportion of people globally who’d received at least one dose of measles-containing vaccine (MCV) increased from 72% to 86%.
JAMA Network reports that during the pandemic however, in 2021, worldwide coverage dropped to 81%, the lowest since 2008. It then rose to 83% in 2022, still not up to the pre-pandemic peak.
In low-income countries, coverage fell from 71% to 67% in 2019-2021 and dropped another percentage point in 2022, the CDC and WHO found.
Although the US MCV coverage is more than 10 percentage points higher than the international average, it had slipped in recent years. From 2019 to 2020, US coverage was 95%, but from 2021 to 2022, it fell to 93%, usually being 95% to 97% nationwide.
Due to missed vaccinations, 2022 saw an 18% increase in estimated measles cases worldwide and a 43% increase in estimated deaths compared with the previous year, the report noted. This translated to about 1.4m additional cases and 41 200 additional deaths.
The decline in measles vaccination rates was probably multi-factorial, said Christopher Hsu, MD, PhD, the lead CDC co-author of the report.
“Some of it may be the anti-vaccination sentiment,” he acknowledged, “but every country is different.”
For example, in some countries, delivery of vaccines to people in remote areas might be challenging.
“What we want to emphasise is that this is a call to action globally for all public health partners. Measles has come back raging in resurgence. We have a highly effective and extremely safe vaccine that needs to be distributed to all children equitably to protect them.”
Half the world’s measles cases occurred in only 10 countries, which the CDC has prioritised, said Hsu, who oversees measles eradication for the WHO’s Eastern Mediterranean Region and South-East Asia Region.
Vaccines
MCV regimens vary from country to country. In the US, measles vaccine is delivered in the same shot as mumps and rubella vaccine (MMR) and, in some cases, varicella vaccine as well (MMRV). But in some countries, it is a stand-alone vaccine or one combined only with rubella (MR vaccine).
Although six of the WHO’s 194 member countries introduced a second dose of MCV in 2022, bringing the total that have done so up to 188, that still leaves six countries where children receive only one dose. “Our ultimate goal globally is to offer at least two measles-rubella doses per child,” Hsu said.
Although a single dose provides protection against measles, two doses are needed to protect against outbreaks. If more than 95% of children worldwide received two doses of MCV, Hsu added, “we can reduce the risk of outbreaks, and we can achieve elimination of measles.”
Infection knows no borders
In the past 30 years, the greatest number of measles cases reported in the US in a single year was 1 274 in 2019, according to the CDC, with nine out of 10 of those cases being in unvaccinated people.
There has also been an increase in non-medical exemptions for vaccination for children.
The MMR and MMRV vaccines are made with weakened live virus, so vaccination could cause potentially life-threatening infections in children with seriously compromised immune systems, the CDC notes.
People in the US and other countries with few cases underestimate the severity of measles and other childhood illnesses, McGowan noted, “because they haven’t seen them, they haven’t seen what they do”.
CDC article – Progress Toward Measles Elimination — Worldwide, 2000–2022 (Open access)
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