I had dengue fever before. I had a fever and severe back pain. Then after a few days, I developed a rash. I was hospitalised and put on a drip. If I had known there was a dengue vaccine, maybe I could have prevented this!

Yes, there is a dengue vaccine, which has just been approved by the US Food and Drug Adminstration (FDA) for use.

But its use comes with severe restrictions.

This vaccine has been used outside the United States since 2015, as dengue is more prevalent in countries like ours than in the US.

Why restrictions?

That’s because after two years of its use in schoolchildren, the Philippines regulatory authorities suspended this vaccine’s use.

The Philippines, a dengue-prevalent country, had used it in 830,000 schoolchildren in a widespread immunisation programme.

But there was early evidence that the vaccine can cause some people who have never had dengue before to possibly have an even more severe version of dengue after vaccination.

I thought vaccines are supposed to prevent the disease. How can a vaccine cause the very disease it is supposed to prevent?

Vaccines are either killed or weakened forms of the microorganisms causing the particular disease the vaccine is suppose to prevent.

They are introduced into your body so that your body can learn the structure of these microorganisms in order to mount an immune response to combat them should you be infected with those microorganisms for real.

Vaccines in large part do NOT cause an infection.

They are there so that your immune system can see them as an “enemy” and “create” specific antibodies in retaliation to their presence.

Some of our immune cells are memory lymphocytes. If our body encounters this microorganism again, these memory cells will be able to quickly produce the specific antibodies to combat the infection before it can take place.

If our body has previously not been exposed to the microroganism via a vaccine, it would take time to “create” the specific antibodies to combat the infection.

In a very few people, the vaccine itself can cause the infection it is supposed to prevent.

This is especially true when the vaccine is made out of weakened microorganisms instead of dead ones. Viral vaccines, for example, are usually made out of weakened viruses, not dead ones.

Vaccines also work to serve the whole community.

Some people cannot be vaccinated for reasons like being too young or too old, or because they are immunocompromised, e.g. those who have a donated organ, cancer, or even diabetes.

So, if everyone else around them is vaccinated, these unvaccinated people will be protected by “herd immunity”.

To put it simply, the unvaccinated person is unlikely to come into contact with the disease because of this herd immunity, so they probably won’t get it.

Oh really? Then how come an entire cinema of moviegoers watching Avengers: Endgame has been told that they have been exposed to measles, just because one person with measles was in the audience?

Measles is on the rise again worldwide because of the actions of some anti-vaccination people, also known as anti-vaxxers, in convincing people not to vaccinate their children.

This is highly irresponsible. Measles, like dengue, can kill children.

The dangers associated with the measles vaccine are very minimal. Compare that to the benefits that a measles vaccine can bring the entire world!

There are so many more lives that can be saved with the vaccine than the very few that it can adversely affect.

Back to the dengue vaccine. What exactly happened in the Philippines?

In 2017, Sanofi, the pharmaceutical company making the dengue vaccine, updated some new data on the vaccine.

Based on six years of clinical data, the new analysis said that the vaccine provides continuous protection for those people who have had a prior dengue infection.

However, for those who have not yet been infected with dengue, there is a risk that they can contract a more severe version of dengue following vaccination, if they are subsequently infected with dengue.

This caused an uproar in the Philippines. Parents were very angry that their children were vaccinated without this prior information.

The Filipino government demanded a multi-million dollar refund from Sanofi, and also a separate fund to cover any serious dengue cases that could result in children after being vaccinated.

It was a very emotional time.

Moreover, some scientists claimed that they had already brought this to everyone’s attention in 2016.

So, should I use the dengue vaccine on my child?

Just go by the label of what is indicated in your country.

Some countries recommend that it should be given for those children nine years and older because younger children are less likely to be exposed to the dengue virus, and hence, forms the population who can develop a more severe illness.

Other countries like Brazil limit it to children 15 years and above. Yet others say only people who have had dengue before should be vaccinated.

The World Health Organization (WHO) itself recommends the vaccine for countries with endemic dengue problems like ours.

Consider this. There are four serotypes of dengue that can infect you.

This means that you can get dengue fever up to four times in your life as the antibodies for each serotype is different.

Every year, there are 390 million dengue infections. Many people actually die from the more severe form of dengue. I myself have had dengue twice!

The choice is up to you to discuss with your doctor the risks versus the benefits of taking the vaccine.

Dr YLM graduated as a medical doctor, and has been writing for many years on various subjects such as medicine, health, computers and entertainment. For further information, email starhealth@thestar.com.my. The information contained in this column is for general educational purposes only. Neither The Star nor the author gives any warranty on accuracy, completeness, functionality, usefulness or other assurances as to such information. The Star and the author disclaim all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.