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


Ancient pathogen is an 'imminent threat' in all parts of the world, WHO warns: ScienceAlert

A consequence 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 missed at least one dose of measles vaccine in 2021.

Measles is a viral respiratory disease. Transmission is similar to COVID, with human-to-human spread driven by respiratory droplets and aerosols (aerosol transmission). In mild cases, the infection causes a rash and fever.

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 vaccination, which can be administered alone or in combination with other vaccinations such as mumps and rubella for the MMR vaccination, is very effective.

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

The vaccine offers very high and long-lasting protection and is truly a paradigm of the term vaccine-preventable disease. The two-dose regimen provides about 99 percent protection against measles infection.

In developing countries, where vaccination is scarce, up to one in ten people with measles die from it. In industrialized countries, mostly unvaccinated people die at a rate of about 1 in 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 like malnutrition greatly increase the risk of serious illnesses, and respiratory infectious diseases are a major concern for humanitarian groups supporting vulnerable groups like Ukrainian refugees.

Measles is incredibly contagious. Its basic reproduction number (R0) — that is, how many people, on average, an infected person infects in a susceptible population — is estimated to be between 12 and 18. For comparison, the R0 of the omicron-COVID variant is assumed to be around 8.2.

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

For measles, 95 percent vaccination coverage is usually considered the magic HIT number.

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

Significant progress has been made worldwide in reducing deaths from all causes in children under the age of five. Annual deaths fell from 12.5 million in 1990 to 5.2 million in 2019. However, low vaccination coverage could wipe out these gains.

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

After a mild case of measles, unvaccinated children lost 33 percent of these antibodies. In comparison, measurements in healthy control populations showed a 10 percent loss of antibodies over similar or longer periods of time.

Misinformation is widespread

Advocacy for vaccination has fueled false rumors and scare stories, such as former doctor and anti-vaccination Andrew Wakefield’s false claims that the MMR vaccine causes autism.

That belief remains. For example, a 2020 US Census Survey found: “18 percent of our respondents incorrectly say it is very or fairly accurate to say that vaccines cause autism.”

Misinformation since the start of the COVID pandemic has been extensive. And there is a risk that this misinformation will further translate into greater hesitation and rejection of routine vaccinations.

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

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

Michael Head, Senior Research Fellow in Global Health, University of Southampton

This article was republished by The Conversation under a Creative Commons license. Read the original article.

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