Science

There is no need for vaccine hesitancy among the young

Let us count our blessing vaccines against so many diseases are available

Although Ireland’s vaccine programme is going well, a significant amount of hesitancy remains. File photograph: iStock

William Reville's face
William Reville
Thu Aug 5 2021 - 01:00

The Covid-19 vaccination programme in Ireland is going well. As I write, 4.1 million doses of vaccine have been administered with 42.6 per cent of eligible people fully vaccinated. Taoiseach Micheál Martin said 70 per cent of adults would be fully vaccinated by the end of July. Nevertheless, a significant amount of vaccine hesitancy remains.

The Irish Examiner reported (on June 21st) that almost 10 per cent of 25- to 35-year-olds will refuse the Covid-19 vaccine and vaccine hesitancy is also high among 18- to 24-year-olds. Many people have genuine doubts about vaccination programmes, wondering if vaccination is necessary at all in the modern world or if they are risky.

I will answer some of the more prominent of these objections to vaccination here. More details are available on the WHO website.

Are vaccines necessary?
Were diseases not already disappearing before vaccines were first introduced because of improved hygiene and sanitation? There is no doubt that improved sanitation, hygiene, nutrition, housing, antibiotics and so on had an indirect influence on disease transmission.

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But, equally, there is no doubt that vaccinations have had a huge direct effect – for example, sanitation is no better now than it was in 1990, when vaccinations against haemophilus influenzae type B (Hib) began. Hib has disappeared in children in recent years in countries with Hib vaccination programmes.

What diseases are most affected by vaccines?
There are many examples. Smallpox was a scourge, killing hundreds of millions globally. It was eradicated in 1979 following a worldwide vaccination programme. Also, incidence of measles dropped permanently coinciding with widespread vaccination starting in 1963. Other vaccine-preventable diseases show similar patterns.

What are the consequences if countries don't vaccinate?
In 1974, whooping cough vaccination rates dropped significantly in the UK due to fears about the vaccine. This precipitated an epidemic of whooping cough with more than 100,000 cases and 36 deaths by 1978. Similar consequences were seen in Japan and Sweden, when vaccination rates dropped. Stop vaccinating and diseases return.

Can vaccines cause disease?
This question may be prompted by the observation that, in a disease outbreak, more vaccinated people may contract the disease than non-vaccinated people. Consider 1,000 children who never had measles. In a high-income country with high vaccination rates, say 994 will be vaccinated against measles and 6 children not vaccinated. Now expose all children to measles. The 6 unvaccinated children will contract measles and maybe 8 vaccinated children also get measles (no vaccine is 100 per cent effective). Now 8 of the 14 children (57 per cent) with measles had been vaccinated. This is actually a vindication of vaccinations. The correct way to look at this is that 100 per cent of unvaccinated children contracted measles, but less than 1 per cent of the vaccinated children got the disease.

What about vaccine side effects?
Vaccines are extremely safe. Most adverse effects reported are very minor – sore arm or a mild fever. More serious events are very rare, occurring at rates between one in thousands and one in millions of vaccinations. This is so rare it is difficult to statistically assess the risk.

What about the link between DTP vaccine and sudden infant death syndrome (SIDS)?
A moderate proportion of children who die of SIDS were recently vaccinated with the diphtheria, tetanus, pertussis (DTP) vaccine. However, most SIDS occurs in the age range when DTP vaccinations are given and the correlation between DTP and SIDS is purely due to chance. All controlled studies show no causal relationship between DTP vaccines and SIDS.

Doesn't even the smallest risk justify avoiding vaccination?
You must consider both risks and benefits. You are far more likely to be seriously injured by the disease than by the vaccine.

Vaccine-preventable diseases are almost gone in many countries – so why vaccinate children?
There is no shortage of disease in many parts of the world and travellers can carry disease into a previously disease-free area, where the disease spreads quickly if people are not vaccinated. Also, some people cannot be vaccinated, for example, because of severe allergic reaction. In order to protect these people, the rest of us must be vaccinated.

We are extremely fortunate to live in a world where vaccines against so many diseases are available and where vaccines against new diseases can be quickly developed. Let us count our blessings.

William Reville is an emeritus professor of biochemistry at UCC

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