What you should know about the various types of vaccines

Travellers especially should take precautions and depending on their destinations, go for the relevant vaccinations

I am often asked about vaccines by my patients; most of the queries pertain to travel, dengue, pneumonia and shingles.

It is interesting to note that most of our childhood vaccines are not compulsory under our laws in Singapore. I had always assumed that vaccines like BCG, polio, hepatitis B, pertussis (whooping cough) are mandatory but only diphtheria and measles are compulsory by law. I believe most parents in Singapore are very compliant with the National Childhood Immunisation Schedule.

In fact, childhood vaccinations have a long history in Singapore. Most people don’t realise that Singapore was one of the first nations in the world to start mass polio vaccination in 1958. We were also one of the first nations to start a mass hepatitis B vaccination programme for all newborns in 1987. As a result, we have managed to cut transmission of Hepatitis B from mother to child by 80 per cent or more. Some of the vaccines are not in the National Immunisation schedule and I am often asked about them. The rotavirus vaccine is for diarrhoea in infants and it is an oral vaccine so there is ease of administering the vaccine. The cost maybe a little daunting though.

The chickenpox vaccine is also useful as chickenpox scars can be quite traumatic for teenagers and everyone does not realise that as an adult, getting shingles is no laughing matter. I am often also asked about the vaccine for cancer of the cervix for young girls. This vaccine is now recommended in the National Schedule. I encourage my patients to send their young daughters for the vaccine as that would prevent cancer of the cervix. The best age would be before they become sexually active; the recommended age would be from 9 years of age onwards. Another vaccine that is quite unusual in the local context – except for people going for the Haj – is the meningitis vaccine. Most of the time, I am asked about this by parents when their child is going to university abroad especially in Europe, USA or Australia/New Zealand. The usual vaccine is called MenAWCY that protects against four strains or serogroups of bacteria identified by the letters.

Increasingly I am also asked by concerned parents about the meningitis B vaccine. At the moment on the CDC Atlanta website, there are three universities in the US that have outbreaks of meningitis B. Apparently there are quite sizeable populations in Western countries carrying the meningitis B strain especially in the varsity age groups. Approximately half of the meningitis cases in the Western world are now caused by this strain.

Another big group of patients are business travellers. A well-paying job in Singapore these days involves a lot of travelling in the region as companies expand overseas. I encourage business travellers to get the influenza vaccine annually. Sometimes the whole family shows up for vaccination prior to a holiday at year end to a winter destination.

This is sadly because they previously had a whole vacation ruined because they caught the flu bug.

Yet other travellers are encouraged to update their Hepatitis A and typhoid vaccines. They are both oralfecal in transmission. Hepatitis A can be quite debilitating, and the natural course may run for up to eight weeks.

Some patients may feel very fatigued for up to six months thereafter. Typhoid fever can be persistent and sometimes diagnosis is delayed; ultimately typhoid can be life threatening. The vaccines are tolerable and there is an oral and injectable typhoid vaccine.

Some of my patients get a fever with the typhoid injectable vaccine but it is usually resolved quickly with paracetamol. As for Hepatitis A, we can also test if the patient is protected against the virus with a simple blood test. About half of those aged 50 and above have natural immunity.

Some of my travellers ask me about tetanus. Most of us have been vaccinated against tetanus in childhood, hence the protection is good enough for a decade till the age of 21 years old. We are actually not worried about stepping on a rusty nail, but whether a wound is dirty. Animal bites are probably the worst and if one fell into a filthy drain, one should get a booster too. A good alternative to the tetanus vaccine is the combined tetanus, diphtheria and pertussis (whooping cough) Tdap vaccine. There is a resurgence of pertussis which is responsible for 10 per cent of emergency room patients presenting with cough.

As for animal bites, I caution travellers not to play with cats, dogs or monkeys when abroad. Singapore is rabies free but the surrounding countries are still endemic for rabies. When bitten abroad, the rabies vaccines and antibody shots should be administered immediately and are both costly and involve multiple injections.

Sometimes, patients ask me about Japanese B encephalitis. This is a disease with high fatality, but you need a mosquito to bite an infected pig and then transmit it to man. Since we have phased out pig farms in Singapore, it is very rare. We would recommend vaccination if one is travelling to certain endemic countries and staying for more than a month in a rural setting. In our local context, there is always the threat of dengue despite our world class mosquito control programme. In dengue infections, we are very concerned if there is a huge viral load coupled with an overwhelming response from the immune system of the patient. This often leads to severe dengue or dengue shock.

The current thinking is that we should vaccinate patients who had dengue previously. The data shows that if we vaccinate dengue-naïve patients; the body becomes primed for severe dengue illness when the infection does occur. In my older patients, I am often asked about pneumonia vaccines and shingles vaccine. The pneumonia vaccines are very useful. There are two available: one covers 13 strains (conjugate PCV13) and the other covers 23 strains (polysaccharide PPV23) of the bacteria that causes pneumonia. We recommend that all above the age of 65 years be vaccinated with both vaccines.

We usually advise that the patient be vaccinated with the conjugate vaccine first followed by the other vaccine a year later. This is to avoid the two vaccines affecting each other’s efficacy. Incidentally the conjugate vaccine is given to children under our national immunisation schedule.

Finally, we have shingles, which is a painful ordeal for patients. Some patients have it on their face and suffer a great deal. There is always the risk of post-shingles pain (post-herpetic neuralgia) that can go on for years. The pain has been known to drive patients to suicide.  The current single dose vaccine is available to those 50 years and older. A newer two-dose shingles vaccine offers very high efficacy, but it is not available yet.

A final word about the naysayers of vaccines; this is also known as vaccine hesitancy. There are many complex reasons for vaccine hesitancy; and social media and Dr Google have not been helpful. There are also the controversies such as Hepatitis B vaccine and multiple sclerosis in France in the 90s and the association of the MMR (measles, mumps and rubella) vaccine and autism. These have been found to be false but the damage has been done. There has been a drop in the coverage of the MMR vaccine in the US and UK with a rise in measles cases worldwide. There is an ongoing measles outbreak in the US originating in the orthodox Jewish communities in New York since October last year. The city has passed a law that prohibits exemptions from vaccines on non-medical grounds. This law will affect 26,000 school-going children in New York. Thankfully in Singapore, vaccine hesitancy has not been a big issue as our population believes that vaccines are safe, effective and necessary.

Dr Chong Yeh Woei
Senior Physician (Internal Medicine)
Singapore Medical Specialists Centre
MBBS (S’pore), MRCP (UK) (Internal Medicine)

The Business Times Weekend, 21 September 2019

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