The World Health Organisation (WHO) has announced global immunisation levels stalled in 2023, leaving many children without life-saving protection.
More than 30 million children in Europe and central Asia were under-protected against measles in 2024, causing serious outbreaks in several countries.
Childhood vaccination rates in Ireland remain below pre-Covid levels and the HSE recently identified Ireland as one of the high-income countries with lower childhood vaccine uptake.
Parents worry about vaccinating their children, vaccine scepticism is growing and some influential people such as US health secretary Robert F Kennedy jnr question vaccine safety. And all this despite the massive evidence that the generally recommended vaccines, including the measles mumps and rubella (MMR) vaccine, are overwhelmingly safe and effective (MMR provides 99 per cent protection).
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Concerns about childhood vaccination, common 50 years ago, faded out over the years but have returned with a bang. We urgently need to allay these concerns.
We are truly blessed in modern society to have easy access to protective vaccinations against a wide range of diseases. In centuries past, before vaccination, people just had to depend on good fortune to avoid contracting serious or deadly diseases. In 17th-century UK, 12 per cent of children died before their first birthday of tetanus, whooping cough, tuberculosis, diphtheria, dysentery, typhus, rickets, chickenpox, scarlet fever, measles, smallpox and the plague.
Much more recently, early in 20th century a deadly viral influenza pandemic unleashed itself on the world – the Spanish flu, lasting from February 1918 to April 1920. There were no effective vaccines or antiviral drugs available to deal with this flu. It infected 500 million people, a third of the world’s population. Estimates of the number killed range from 50 million to 100 million.
But today, UK babies are vaccinated against potentially life-threatening diseases and the infant mortality rate is 0.36 per cent. The WHO estimates that vaccination saved 10 million lives globally between 2010 and 2015.
When a high percentage of the population is vaccinated, infectious diseases find it difficult to spread because so few people can be infected – “herd immunity”. If someone with measles is surrounded by people who are vaccinated against measles, the disease cannot easily pass on to anyone, and it will quickly disappear again. Herd immunity protects vulnerable people such as newborn babies, older people and those too sick to be vaccinated. Nineteen out of 20 people need to be vaccinated to achieve herd immunity against measles.
Over recent decades, effective mass-vaccination programmes became widely accepted. So, why are so many people now questioning the safety of vaccines and showing reluctance to vaccinate both themselves and their children? It seems to me we grew so used to widespread protection afforded by vaccination that we became blasé and started to entertain the cognitive biases that always lurk in the background.
The common cognitive biases include vaccine mistrust; risk perception, forgetting vaccination is a public good, confirmation bias and the illusion of causality.
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Vaccine mistrust: some people refuse vaccines because they distrust the big pharma companies that develop the vaccines and worry about side effects of vaccination.
Risk perception: some people think the risks posed by the vaccine exceed the risk of getting seriously ill; for example, many cases of measles have only mild symptoms. However, a minority of cases result in blindness or deafness and some children die. This is the risk if you don’t get your child vaccinated.
Public good: some people don’t understand the more people who get vaccinated, the greater the protection afforded to everybody.
Confirmation bias: people tend to seek out information supporting their beliefs and spurn information that rejects their beliefs.
Public health bodies must mount vigorous campaigns to counter these cognitive biases. Of course, I’m not saying all criticism of vaccines must be mistaken. No scientific field is immune from error.
Criticism should be listened to but the critics should be required to publicly present their case and their evidence. Expert immunologists should also publicly present the case underpinning current policies.
Since current practice is based on massively convincing evidence, it will mostly win the argument. But occasionally there will be something of value in the criticism and this should be taken on board.
William Reville is an emeritus professor of biochemistry at UCC
