We know vaccines have been a miracle for public health. Now, new research led by the World Health Organization has found vaccines have saved an estimated 154 million lives in the past 50 years from 14 different diseases. Most of these have been children under five, and around two-thirds children under one year old.

In 1974 the World Health Assembly launched the Expanded Programme on Immunization with the goal to vaccinate all children against diphtheria, tetanus, pertussis (whooping cough), measles, polio, tuberculosis and smallpox by 1990. The program was subsequently expanded to include several other diseases.

The modelling, marking 50 years since this program was established, shows a child aged under ten has about a 40% greater chance of living until their next birthday, compared to if we didn’t have vaccines. And these positive effects can be seen well into adult life. A 50-year-old has a 16% greater chance of celebrating their next birthday thanks to vaccines.

What the study did

The researchers developed mathematical and statistical models which took in vaccine coverage data and population numbers from 194 countries for the years 1974–2024. Not all diseases were included (for example smallpox, which was eradicated in 1980, was left out).

The analysis includes vaccines for 14 diseases, with 11 of these included in the Expanded Programme on Immunization. For some countries, additional vaccines such as Japanese encephalitis, meningitis A and yellow fever were included, as these diseases contribute to major disease burden in certain settings.

The models were used to simulate how diseases would have spread from 1974 to now, as vaccines were introduced, for each country and age group, incorporating data on increasing vaccine coverage over time.

Children are the greatest beneficiaries of vaccines

Since 1974, the rates of deaths in children before their first birthday has more than halved. The researchers calculated almost 40% of this reduction is due to vaccines.

The effects have been greatest for children born in the 1980s because of the intensive efforts made globally to reduce the burden of diseases like measles, polio and whooping cough.

Some 60% of the 154 million lives saved would have been lives lost to measles. This is likely due to its ability to spread rapidly. One person with measles can spread the infection to 12–18 people.

The study also found some variation across different parts of the world. For example, vaccination programs have had a much greater impact on the probability of children living longer across low- and middle-income countries and settings with weaker health systems such as the eastern Mediterranean and African regions. These results highlight the important role vaccines play in promoting health equity.

Vaccine success is not assured

Low or declining vaccine coverage can lead to epidemics which can devastate communities and overwhelm health systems.

Notably, the COVID pandemic saw an overall decline in measles vaccine coverage, with 86% of children having received their first dose in 2019 to 83% in 2022. This is concerning because very high levels of vaccination coverage (more than 95%) are required to achieve herd immunity against measles.

In Australia, the coverage for childhood vaccines, including measles, mumps and rubella, has declined compared to before the pandemic.

This study is a reminder of why we need to continue to vaccinate – not just against measles, but against all diseases we have safe and effective vaccines for.

The results of this research don’t tell us the full story about the impact of vaccines. For example, the authors didn’t include data for some vaccines such as COVID and HPV (human papillomavirus). Also, like with all modelling studies, there are some uncertainties, as data was not available for all time periods and countries.

Nonetheless, the results show the success of global vaccination programs over time. If we want to continue to see lives saved, we need to keep investing in vaccination locally, regionally and globally.

Meru Sheel, Associate Professor and Epidemiologist, Infectious Diseases, Immunisation and Emergencies Group, Sydney School of Public Health, University of Sydney and Alexandra Hogan, Mathematical epidemiologist, UNSW Sydney

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

We know the importance of staying hydrated, especially in hot weather. But even for something as simple as a drink of water, conflicting advice and urban myths abound.

Is cold water really bad for your health? What about hot water from the tap? And what is “raw water”? Let’s dive in and find out.

Myth 1: Cold water is bad for you

Some recent TikToks have suggested cold water causes health problems by somehow “contracting blood vessels” and “restricting digestion”. There is little evidence for this.

While a 2001 study found 51 out of 669 women tested (7.6%) got a headache after drinking cold water, most of them already suffered from migraines and the work hasn’t been repeated since.

Cold drinks were shown to cause discomfort in people with achalasia (a rare swallowing disorder) in 2012 but the study only had 12 participants.

For most people, the temperature you drink your water is down to personal preference and circumstances. Cold water after exercise in summer or hot water to relax in winter won’t make any difference to your overall health.

Myth 2: You shouldn’t drink hot tap water

This belief has a grain of scientific truth behind it. Hot water is generally a better solvent than cold water, so may dissolve metals and minerals from pipes better. Hot water is also often stored in tanks and may be heated and cooled many times. Bacteria and other disease-causing microorganisms tend to grow better in warm water and can build up over time.

It’s better to fill your cup from the cold tap and get hot water for drinks from the kettle.

Myth 3: Bottled water is better

While bottled water might be safer in certain parts of the world due to pollution of source water, there is no real advantage to drinking bottled water in Australia and similar countries.

According to University of Queensland researchers, bottled water is not safer than tap water. It may even be tap water. Most people can’t tell the difference either. Bottled water usually costs (substantially) more than turning on the tap and is worse for the environment.

What about lead in tap water? This problem hit the headlines after a public health emergency in Flint, Michigan, in the United States. But Flint used lead pipes with a corrosion inhibitor (in this case orthophosphate) to keep lead from dissolving. Then the city switched water sources to one without a corrosion inhibitor. Lead levels rose and a public emergency was declared.

Fortunately, lead pipes haven’t been used in Australia since the 1930s. While lead might be present in some old plumbing products, it is unlikely to cause problems.

Myth 4: Raw water is naturally healthier

Some people bypass bottled and tap water, going straight to the source.

The “raw water” trend emerged a few years ago, encouraging people to drink from rivers, streams and lakes. There is even a website to help you find a local source.

Supporters say our ancestors drank spring water, so we should, too. However, our ancestors also often died from dysentery and cholera and their life expectancy was low.

While it is true even highly treated drinking water can contain low levels of things like microplastics, unless you live somewhere very remote, the risks of drinking untreated water are far higher as it is more likely to contain pollutants from the surrounding area.

Myth 5: It’s OK to drink directly from hoses

Tempting as it may be, it’s probably best not to drink from the hose when watering the plants. Water might have sat in there, in the warm sun for weeks or more potentially leading to bacterial buildup.

Similarly, while drinking water fountains are generally perfectly safe to use, they can contain a variety of bacteria. It’s useful (though not essential) to run them for a few seconds before you start to drink so as to get fresh water through the system rather than what might have been sat there for a while.

We are fortunate to be able to take safe drinking water for granted. Billions of people around the world are not so lucky.

So whether you like it hot or cold, or somewhere in between, feel free to enjoy a glass of water this summer.

Just don’t drink it from the hose.

Oliver A.H. Jones, Professor of chemistry, RMIT University

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