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Children's Health 2019

Vaccine hesitancy and the threat to global health

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Dr Ann Hogan

Former President, Irish Medical Organisation (IMO) and Chair, IMO Public and Community Health Committee

Vaccine hesitancy has been identified by the World Health Organization as one of the top 10 threats to global health. Here, Dr Ann Hogan debunks some of the myths that are leading to vaccine hesitancy and highlights the evidence that shows that vaccines work.


Vaccine hesitancy is the growing reluctance of individuals to get vaccinated or to vaccinate their children and threatens to reverse the progress made in vaccine preventable disease.

Vaccination currently prevents two to three million deaths worldwide every year and a further 1.5 million deaths every year could be avoided if vaccine coverage improved.

Vaccination has brought about the elimination of smallpox, a viral infection, which, in the past, was a very common cause of illness and death (30% of cases), especially in children. Smallpox has been declared eradicated, worldwide since 1980.

Major outbreaks of ‘eradicated’ diseases

Diphtheria, tetanus and polio were common causes of illness and death. Since the introduction of vaccines against these diseases, their incidence in Ireland has declined to minimal levels.

However, we know that keeping these diseases under control is dependent on high vaccine uptake. When vaccination uptake declined in the Russian Federation in the 1990s, there was a major outbreak of diphtheria and over 150,000 cases and 4,500 deaths were reported.

Other vaccines introduced into the Irish primary childhood vaccination programme have resulted in decline in incidence of whooping cough (pertussis), rubella, mumps, measles, various forms of bacterial meningitis and rotavirus infection.

MMR vaccine: Side-effects of not vaccinating vs side-effects of vaccinating

We know that the MMR (measles, mumps, rubella) vaccine is highly effective against measles, with 99% of people developing immunity to measles after two doses of MMR. But we are seeing outbreaks of measles in Ireland and in several countries in Europe where MMR is part of the routine childhood immunisation schedule.

The viruses and bacteria that cause these infectious diseases have not gone away and, as we are seeing with measles at present, outbreaks will occur when uptake of vaccinations falls below optimal levels.

There is no cause for complacency about these diseases. Many people express concern about side-effects of vaccination. Vaccines do have side-effects, some of which are serious. However, the side-effects associated with getting the actual diseases are far worse than the side-effects of the vaccines.

If 1,000 children get measles:

  • 160 will get diarrhoea
  • 50 will get an ear infection
  • 40 will get a chest infection
  • five will have convulsions
  • one will develop encephalitis, which may result in brain damage or death.

One in 8,000 children who get measles under the age of two will go on to develop SSPE (brain degeneration) several years afterwards.

If 1,000 children get the MMR vaccine:

  • 100 will get redness and swelling at the injection site or will have a fever
  • 50 will get a rash 5-10 days after vaccination
  • one will have a convulsion
  • one in 10 million will develop encephalitis.
  • one in 22,000 will get a temporary blood clotting problem.

Misinformation through social media

Circulation of anti-vaccination information has been going on since smallpox vaccination was introduced over 200 years ago. Unfortunately, modern social media has made it easier than ever before to circulate information and misinformation, including misinformation about vaccines.

It is sad when outbreaks of previously-controlled infectious diseases occur in situations of war or other major events, but it is worse when vaccination uptake falls as a result of complacency or false concerns about side-effects.

Vaccines work. They prevent millions of deaths, mainly in children, every year.

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