Ancient pathogen is an 'imminent threat' in all regions of the world, WHO warns

Ancient pathogen is an ‘imminent threat’ in all regions of the world, WHO warns

One of the consequences of the pandemic has been reduced access to routine health care and reduced uptake of vaccinations. As a result, in November 2022, the World Health Organization declared measles an “imminent threat in all regions of the world”.

They described how a record number of nearly 40 million children had missed at least one dose of the measles vaccine in 2021.

Measles is a viral respiratory disease. Transmission is similar to COVID, with spread between people driven by respiratory droplets and aerosols (airborne transmission). The infection produces a rash and fever in mild cases.

But severe cases can include encephalitis (swelling of the brain), blindness and pneumonia. There are approximately 9 million cases per year and 128,000 deaths.

The measles vaccine, which can be given alone or in combination with other vaccines such as mumps and rubella to complement the MMR vaccine, is very effective.

Most countries have a two-dose schedule, with the first shot usually given when the child is 12 months old and the second dose when the child is four years old.

The vaccine provides very high and long-lasting protection, and is truly a model example of the phrase “vaccine-preventable disease.” The two-dose regimen provides approximately 99% protection against measles infection.

In developing countries where immunization coverage is low, up to one in ten people who catch measles die from it. In developed countries, deaths are mostly among unvaccinated people, at a rate of about one in every 1,000 to 5,000 measles cases.

The potential for new outbreaks of vaccine-preventable diseases in areas such as conflict zones and among refugee populations is high.

Issues such as malnutrition dramatically increase the risk of serious illness, and respiratory infectious diseases are a major concern for humanitarian groups supporting vulnerable groups such as Ukrainian refugees.

Measles is incredibly contagious. Its basic reproduction number (R0) – that is, the average number of people an infected person will infect in a susceptible population – is estimated to be between 12 and 18. For comparison, it is thought that the R0 of the omicron COVID variant to be around 8.2.

The proportion of a population that must be vaccinated to control outbreaks and minimize transmission in a community is known as the herd immunity threshold (HIT).

For measles, 95% vaccination coverage is generally considered the magic HIT number.

Most of the world is well below this threshold, with global coverage of around 71% for two doses and 81% for one-dose coverage. In the UK, data from 2021-22 shows that 89% of children had received a dose of measles vaccine.

Globally, significant progress has been made in reducing deaths from all causes among children under five. Annual deaths have fallen from 12.5 million in 1990 to 5.2 million in 2019. However, low vaccination coverage could reverse these gains.

Even if children survive measles, there is a possibility of long-term damage to their immune system, described as a “form of immune amnesia”. In unvaccinated populations, a severe case of measles caused an average loss of 40% of the antibodies that would normally recognize the germs.

After a mild case of measles, unvaccinated children lost 33% of these antibodies. In comparison, measurements in healthy control populations indicated a 10% antibody loss over similar or longer durations.

Misinformation is commonplace

Anti-vaccine advocacy has sparked false rumors and scare stories, such as former doctor and anti-vaccine activist Andrew Wakefield’s false claims that the MMR vaccine causes autism.

This belief persists. For example, a 2020 US population survey found, “18% of our respondents incorrectly state that it is very or somewhat accurate to say that vaccines cause autism.”

The misinformation since the start of the COVID pandemic has been extensive. And there is a risk that this misinformation will translate into higher levels of vaccine hesitancy and refusal for routine immunization.

Measles spreads easily and is a serious short- and long-term infection in unvaccinated populations. There is a great need for vaccination campaigns to increasingly protect against vaccine-preventable diseases around the world.

The need is particularly urgent in developing countries and among other vulnerable populations such as refugees and conflict zones.The conversation

Michael Head, Senior Researcher in Global Health, University of Southampton

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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