Both senior citizens and young children can have suboptimal immune systems that make them more vulnerable to infectious diseases such as RSV. — 123rf
It is estimated that around 90% of adults aged 50 and above have been infected with the varicella-zoster virus.
If you ever had chickenpox, then this wily virus is lurking in your nervous system even as you read this.
Although the extremely itchy blisters that are the hallmark of chickenpox do eventually go away, this doesn’t mean that the virus that caused them has also disappeared.
Instead, the varicella-zoster virus goes into hiding in our sensory nerves, awaiting an opportunity to slip past the guard of our immune system and wreak havoc again.
And the havoc it can cause is even worse the second time around as it affects our nerves, resulting in the extremely painful blisters of shingles.
The odds of a person’s immune system letting their guard down is actually quite high, occurring in one in three previous chickenpox sufferers.
And the risk of this happening increases with age (especially after 50 years), a compromised immune system (e.g. in HIV and cancer patients), an autoimmune disease (e.g. rheumatoid arthritis and inflammatory bowel disorder) and chronic conditions (e.g. diabetes, heart disease, asthma and depression).
There is no cure for shingles (or chickenpox); doctors can only offer supportive treatment to help ease the symptoms.
Fortunately, both conditions do have vaccines available.
According to the Malaysian Society of Infectious Diseases and Chemotherapy, there are three vaccines currently available in Malaysia for chickenpox.
Two of these are specifically for chickenpox, and are given in two doses by injection under the skin.
The other one is a combination vaccine, which incorporates the measles, mumps and rubella (MMR) vaccine along with the chickenpox one.
This vaccine, however, is only approved for use in children aged one to 12 years.
According to the US Centres for Disease Control and Prevention (CDC), the effectiveness of the chickenpox vaccines in preventing the infection ranges between 88% to 98%.
And for the small minority who still developed the infection after vaccination, the symptoms tended to be much milder than a typical case.
There is also one vaccine currently available for shingles.
Launched in Malaysia in September (2024), this vaccine was found to be 97% effective in preventing shingles in those aged 50 to 69 years, and 91% effective in those aged 70 and above.
Results from the long-term follow-up phase III clinical trial for this vaccine, which were released in April (2024), showed that the vaccine efficacy was still high at 82% for adults 50 years and older, 10 years after their vaccination.
Affecting babies and seniors
Another virus that tends to have more serious consequences at the extremes of age is the respiratory syncytial virus (RSV).
Infection with this highly-transmissible virus (one infected person can infect up to three other people) can occur at any age, and is usually mild and self-limiting.
Like the common cold and influenza, there is no cure for this condition and doctors can only provide supportive treatment to ease any symptoms while your body fights off the virus by itself.
Because of this, it can develop into a serious infection in young children whose immune systems are not mature yet, older people whose immune systems are starting to age and function less well, as well as those who have compromised or weakened immune systems due to other medical conditions.
According to GSK RSV Global Medical Affairs medical director Dr Elisa Turriani, RSV is the most common cause of hospitalisation in infants, and also causes significant illness in children aged below five years.
“What most of us don’t know – and what I didn’t know until I started working on this – is that you continue to get RSV throughout your life.
“We are continuously infected multiple times because the immunity that is given by the natural infection is only short-lived.
“And as we get older, the fact that we continue to get the disease actually can become quite dangerous – because as we get older, our immune system ages and we are more likely to get a severe RSV infection,” she told international media at a briefing in GSK’s vaccine manufacturing site in Wavre, Belgium.
For example, RSV can result in complications like pneumonia, as well as the worsening of chronic conditions like asthma and heart disease, leading to hospitalisation, and even death.
She also points out that research is showing that older adults are being hospitalised, and dying, of RSV at far higher rates than young children.
And that these statistics are likely to be undercounted as older patients are less likely to be tested for this infection.
RSV however, is one of the infectious diseases that have various vaccines both on the market and in development.
Indeed, one RSV vaccine targetted at adults aged 60 and above was launched September (2024) in Malaysia.
According to data from its phase III clinical trials, the vaccine showed an 82.6% protective effect against lower respiratory tract disease (e.g. pneumonia) for healthy adults aged 60 and above, after one RSV season.
This protection went up to 94.6% for adults aged 60 and above, who had one or more concurrent medical conditions (co-morbidities).
In temperate countries, an RSV season usually starts in autumn and lasts until the end of winter.
In Malaysia, the threat of RSV lasts throughout the year, with peaks in July-August and October-December.
The latest data however, shows that the effectiveness of the one-dose vaccine drops to 48% for the healthy adults, and 57.8% for those with at least one co-morbidity, after the third RSV season.
The other prophylactic (preventive) treatment available in Malaysia is specifically for young children aged eight to 19 months who are at increased risk for severe RSV.
These include premature babies with chronic lung disease, severely immunocompromised young children and those with cystic fibrosis.
This expensive treatment is an injected monoclonal antibody called nirsevimab, which helps prevent severe RSV disease in these young children.
