The much-awaited winter in Thailand, which officially began last month according to the Meteorological Department, brings with it not just a short-lasting cool breeze but also the spread of the influenza virus.
The Ministry of Public Health was quick to warn people of the first line of defence against the disease, which includes frequent hand-washing, not sharing personal materials with flu patients, avoiding crowded places where the risk of receiving the virus can be high, and of course, getting a flu shot.
But when it comes to the vaccine, doubt still looms especially as to its cost-effectiveness -- is the shot really worth it when some people still fall ill even though they have been vaccinated against the flu virus?
Infectious medicine specialist Dr Chanunya Srihawan urged consumers to understand that there are actually certain factors that attribute to the fact that people are still likely to succumb to the influenza virus despite being vaccinated.
"First, there is no such thing as a vaccine that is 100% protective," she explained. "Second, the influenza virus itself is quite tricky. It develops and mutates. It shifts at the genetic level, sometimes to the point that it becomes strong enough to stand against the vaccine's protection."
The flu virus has wreaked havoc in Thailand this year. According to figures from the Bureau of Emerging Infectious Diseases under the Ministry of Public Health's Department of Disease Control, around 165,000 Thais have fallen prey to influenza since the beginning of this year. The disease killed 43 people this year. The Ministry of Public Health speculates that there will be 50,000 more cases this winter and subsequently encouraged healthcare personnel and service providers to be more vigilant especially in disaster-affected areas.
The surging number of flu cases during the cold season gives a clear picture of the epidemic pattern in Thailand where, according Dr Chanunya, the virus usually spreads during the rainy season, from June until October, and again in winter, from year-end to March. Out of these two periods, flu cases are still sporadically found, unlike in such western countries as in the United States where the virus typically spreads during late autumn and winter from September to March.
Since it would take about two weeks after the flu shot to get the body readily immunised, people are advised to receive the vaccine shortly prior to the flu season so that it takes full effect when the time comes.
"The vaccine is the same all over the world but people in the northern and southern hemisphere are recommended to get the shot at a different times," the specialist said. "People in the northern hemisphere [such as those in Europe and America] are advised to be vaccinated around August-September. Countries in the south, including Thailand should have the vaccine around April to May, before entering the rainy season."
The World Health Organisation (WHO) has continuously made an effort to put influenza under the global spotlight. This year, for example, marks the 20th anniversary of FluNet, a global web-based reporting and analysis platform for influenza surveillance first launched by the WHO in 1997. The database allows national influenza centres around the world to share laboratory data among themselves and with the WHO on a weekly basis.
Every year, the WHO issues its recommended composition of influenza virus vaccines for use in the following year. For 2018, the recommendation for the southern hemisphere was released in September, while the northern hemisphere's recommendations were announced in March. Based on data from different sources, networks and studies, the WHO's recommendation aims to provide a guide to national public health authorities and vaccine manufacturers to follow its protocol for the production of the flu vaccine for the next flu season.
The influenza vaccines that are available in the market right now can be divided into two types: quadrivalent vaccines that protect against four flu strains and trivalent vaccines that shield against three. The former contains two influenza A viruses and two B viruses while the latter contains two influenza A viruses and one B virus. The influenza A is more commonly found. But the severity and symptoms of both strains are quite similar -- headaches, high fever, coughing, sore throat, runny nose, nausea, vomiting and diarrhoea.
For consumers, it is important to understand that the influenza vaccine produced based on the WHO's recommendation doesn't provide a 100% protection against each of the four or three flu strains.
"The level of protection of each virus strain in the vaccine does vary," explained Dr Chanunya. "Mostly the vaccine can render 70% protection against the influenza B viruses. For the A viruses, different reports show different data. Some say 35%, 50% or can be up to 70%"
And because there are actually hundreds of influenza virus strains spread across the world, those vaccinated still have chances of getting infected with other strains.
"Several factors are responsible for people falling sick even after having the vaccine. First, the body receives the virus when the immunity level lowers. Or second, the body receives the virus in high amounts probably because that person stays in a very close contact with patients. And third, the body is infected with a subtype of influenza virus that is not included in the vaccine."
Is it then possible that one day the world will have a super-effective vaccine that can protect against all influenza subtypes?
"The virus itself keeps developing making it perhaps impossible to create a vaccine that protects against everything. It's like we are playing chase and catch. Each year we predict the virus subtypes [that could become an epidemic] and create a vaccine. But at the same time the virus is changing this and that in itself, trying to escape what we have in the shot. And it goes in loop like this," Dr Chanunya said.
Despite all these limitations, the WHO still lists and recommends the influenza vaccination as the most effective way to prevent the illness. Dr Chanunya concurs.
"Personally, I think it's worth having the shot. Although in some cases it's not 100% effective, at least it enables the body to be immunised to a certain extent, which can help reduce the severity and complications caused by the flu virus."
"The influenza vaccine is a kind of protection which is recommended globally. It protects you from the risk that even doctors cannot foresee," she added.
Apart from the flu shot, what's equally fundamental, according to Dr Chanunya, is personal protection. One of the reasons, she said, why people are still infected despite having the vaccine is because they do not protect themselves well enough.
"Personal hygiene and protection is a huge issue. If you do it well, you will never get infected even without the vaccine. On the contrary, when a family member is diagnosed as having influenza, other family members do not know how to prevent the virus from spreading. Your immunised body will definitely not be able to stand if you are exposed to a high amount of the virus or stay in a very close contact with patients. Vaccine is one thing. But personal protection is equally and sometimes even more essential."
