The Therapeutic Goods Administration (TGA) has approved a vaccine against respiratory syncytial virus (RSV) in Australia for the first time. The shot, called Arexvy and manufactured by GSK, will be available by prescription to adults over 60.

RSV is a contagious respiratory virus which causes an illness similar to influenza, most notably in babies and older adults.

So while it will be good to have an RSV vaccine available for older people, where is protection up to for the youngest children?

A bit about RSV

RSV was discovered in chimpanzees with respiratory illness in 1956, and was soon found to be a common cause of illness in humans.

There are two key groups of people we would like to protect from RSV: babies (up to about one year old) and people older than 60.

Babies tend to fill up hospitals during the RSV season in late spring and winter in large numbers, but severe infection requiring admission to intensive care is less common.

In babies and younger children, RSV generally causes a wheezing asthma-like illness (bronchiolitis), but can also cause pneumonia and croup.

Although there are far fewer hospital admissions among older people, they can develop severe disease and die from an infection.

RSV vaccines for older people

For older adults, there are actually several RSV vaccines in the pipeline. The recent Australian TGA approval of Arexvy is likely to be the first of several, with other vaccines from Pfizer and Moderna currently in development.

The GSK and Pfizer RSV vaccines are similar. They both contain a small component of the virus, called the pre-fusion protein, that the immune system can recognise.

Both vaccines have been shown to reduce illness from RSV by more than 80% in the first season after vaccination.

In older adults, side effects following Arexvy appear to be similar to other vaccines, with a sore arm and generalised aches and fatigue frequently reported.

Unlike influenza vaccines which are given each year, it is anticipated the RSV vaccine would be a one-off dose, at least at this stage.

Protecting young children from RSV

Younger babies don’t tend to respond well to some vaccines due to their immature immune system. To prevent other diseases, this can be overcome by giving multiple vaccine doses over time. But the highest risk group for RSV are those in the first few months of life.

To protect this youngest age group from the virus, there are two potential strategies available instead of vaccinating the child directly.

The first is to give a vaccine to the mother and rely on the protective antibodies passing to the infant through the placenta. This is similar to how we protect babies by vaccinating pregnant women against influenza and pertussis (whooping cough).

The second is to give antibodies directly to the baby as an injection. With both these strategies, the protection provided is only temporary as antibodies wane over time, but this is sufficient to protect infants through their highest risk period.

Abrysvo, the Pfizer RSV vaccine, has been trialled in pregnant women. In clinical trials, this vaccine has been shown to reduce illness in infants for up to six months. It has been approved in pregnant women in the United States, but is not yet approved in Australia.

An antibody product called palivizumab has been available for many years, but is only partially effective and extremely expensive, so has only been given to a small number of children at very high risk.

A newer antibody product, nirsevimab, has been shown to be effective in reducing infections and hospitalisations in infants. It was approved by the TGA in November, but it isn’t yet clear how this would be accessed in Australia.

What now?

RSV, like influenza, is a major cause of respiratory illness, and the development of effective vaccines represents a major advance.

While the approval of the first vaccine for older people is an important step, many details are yet to be made available, including the cost and the timing of availability. GSK has indicated its vaccine should be available soon. While the vaccine will initially only be available on private prescription (with the costs paid by the consumer), GSK has applied for it to be made free under the National Immunisation Program.

In the near future, we expect to hear further news about the other vaccines and antibodies to protect those at higher risk from RSV disease, including young children.

Allen Cheng, Professor of Infectious Diseases, Monash University

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

Water is essential for daily functioning and health, and we can only survive a few days without it. Yet we constantly lose water through sweat, urination and even evaporation when we breathe.

This is why we have evolved a way to regulate and maintain water in our bodies. Like other animals, our survival relies on a strong biological drive that tells us to find and drink water to balance fluid loss.

This is thirst – a sensation of dryness in the mouth signalling we need to have a drink. This basic physiological mechanism is controlled mainly by part of the brain’s “control centre”, called the hypothalamus. The hypothalamus receives signals from various regions of the body and in return, releases hormones that act as a messenger to signal the thirst sensation.

What is dehydration?

Staying hydrated (having enough water in our bodies) is important for several reasons, including:

• regulating body temperature through sweat and respiration
• lubricating joints and eyes
• preventing infections
• digesting and absorbing nutrients
• flushing out waste (via the kidneys)
• preventing constipation
• brain function (including memory and concentration)
• mood and energy levels
• physical performance and recovery from exercise
• skin health.

Dehydration occurs when our body doesn’t have enough water. Even slight drops in fluid levels have noticeable consequences, such as headaches, feeling dizzy, lethargy and struggling to concentrate.

Chronic dehydration can pose more serious health risks, including urinary tract infections, constipation and kidney stones.

What does the evidence say?

Despite thirst being one of the most basic biological drivers for good hydration, science suggests our feelings of thirst and subsequent fluid intake don’t always correlate with hydration levels.

For example, a recent study explored the impact of thirst on fluid intake and hydration status. Participants attended a lab in the morning and then later in the afternoon to provide markers of hydration status (such as urine, blood samples and body weight). The relationship between levels of thirst in the morning and afternoon hydration status was negligible.

Further, thirst may be driven by environmental factors, such as access to water. For example, one study looked at whether ample access to water in a lab influenced how much people drank and how hydrated they were. The link between how thirsty they felt and how hydrated they were was weak, suggesting the availability of water influenced their fluid intake more than thirst.

Exercise can also change our thirst mechanism, though studies are limited at this stage.

Interestingly, research shows women experience thirst more strongly than men, regardless of hydration status. To understand gender differences in thirst, researchers infused men and women with fluids and then measured their thirst and how hydrated they were. They found women generally reported thirst at a lower level of fluid loss. Women have also been found to respond more to feeling thirsty by drinking more water.

Other ways to tell if you need to drink some water

While acknowledging some people will need to drink more or less, for many people, eight cups (or two litres) a day is a good amount of water to aim for.

But beyond thirst, there are many other ways to tell whether you might need to drink more water.

1. urine colour: pale yellow urine typically indicates good hydration, while darker, concentrated urine suggests dehydration

2. frequency of going to the toilet: urinating regularly (around four to six times a day) indicates good hydration. Infrequent urination can signal dehydration

3. skin turgor test: gently pinching the skin (for example, on the back of the hand) and observing how quickly the skin returns to its normal position can help assess hydration. Slow return may indicate dehydration

4. mouth and lips: a dry mouth or cracked lips can be early signs of dehydration

5. headaches and fatigue: frequent headaches, dizziness, or unexplained fatigue can be signs of inadequate hydration

6. sweating: in physically active people, monitoring how much they sweat during activity can help estimate fluid loss and hydration needs. Higher levels of sweat may predispose a person to dehydration if they are unable to replace the fluid lost through water intake

These indicators, used together, provide a more comprehensive picture of hydration without solely depending on the sensation of thirst.

Of course, if you do feel thirsty, it’s still a good idea to drink some water.

Lauren Ball, Professor of Community Health and Wellbeing, The University of Queensland and Kiara Too, PhD candidate, School of Human Movement and Nutrition Sciences, The University of Queensland

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