Wednesday, April 22, 2009

STI: Vaccine's mixed signals

April 23, 2009

Doc talk

Vaccine's mixed signals

By Dr Ang Peng Tiam 


Recently, many patients, friends and acquaintances have asked me about 'the cancer vaccine". It seems to work like magic: take a shot and you will be protected from cervical cancer.


For me, the answer is quite straightforward. However, if it is such a no-brainer, why is there some reluctance to having compulsory vaccination of pre-teens?


First, we must recognise that it is true that women with many sex partners are at increased risk of getting cancer of the cervix. The causative agent in 90 per cent of cervical cancer patients is the human papilloma virus (HPV). There are many strains of HPV infections and some of the ones more commonly associated with cervical cancer are subtypes 16, 18, 31 and 45.


Establishing the link between HPV infection and cervical cancer and the discovery of not one but two vaccines against HPV have opened up one more strategy for tackling this cancer.


If all women were vaccinated against HPV before they become sexually active, the prevalence of HPV infection in the vaccinated community would be lowered. In turn, the risk of getting HPV-related cervical cancer would also diminish.


All this stems from the fact that HPV infection is a sexually transmitted disease. Women who have only one sex partner are relatively safe. Whether they acquire HPV infection depends largely on whether the male partner is infected or not. In other words, no sex equals no infection.


So, here is the difficult question. By vaccinating young girls at the age of 12 or 14, are we sending the correct message?


Let's not forget that ours is a relatively conservative society. By vaccinating them at that age, are we indirectly saying that it is all right for them to engage in sexual activity? Isn't there a law against having sex with a minor (anyone below the age of 16)?


Secondly, we must remember that even though the vaccine may protect our daughters against HPV infection, there are other viruses, such as the human immunodeficiency virus (HIV), which are also transmitted through sexual contact. By vaccinating the young against HPV, will it lull them into a sense of complacency and indirectly endanger their lives? Should not the message be one of abstinence or proper use of the condom?


As an oncologist, I would like to see HPV infection eradicated or minimised, so that the incidence of cervical cancer will go down. However, I have some concerns that introducing compulsory vaccination will indirectly endorse casual sex.


Somehow, I feel that each parent has to decide for himself when it is most appropriate for his daughter to be vaccinated. Ideally, the time for vaccination should be six months before she has her first sexual contact.


So, if this contact takes place when the woman is already grown, say, before her marriage, this decision truly is a no-brainer. One woman dies every five days from cancer of the cervix and one woman is diagnosed every two days.


The primary focus when tackling this cancer has always been that of screening. The cervix is in a very accessible site. It can be inspected through a speculum (beak-like device which opens up the vagina for direct visualisation) and can be felt through digital examination.


More importantly, the cells from the cervix can be scraped off (Pap smear) and examined under the microscope for changes in appearance. These changes are classified to indicate varying levels of suspicion of cancer change.


Women who go routinely for a Pap smear should not die from cervical cancer. In fact, this is one cancer that can easily be diagnosed when it is pre-cancerous (called carcinoma-in-situ). With early intervention, involving either removal of a part of the cervix or the entire womb, patients are invariably cured of the disease.


The sad truth is that despite decades of public education, many women have either never gone for Pap smear testing or do not go as regularly as they should.


I have often asked my patients why they have not been compliant. They have given me many reasons, including how they feel it is a hassle to go and see a doctor for 'just a check-up" when they feel nothing is wrong. Being examined 'down there" is also not comfortable both physically and psychologically.


Many also hold the belief that cancer cannot happen to them. After all, isn't cancer of the cervix something that happens only to promiscuous women with multiple sex partners? Sadly, this is not true. It can happen to anyone, as long as her male partner carries the virus.


The solution, again, is medically simple. However, as we know, the intricacies of human behaviour are far more complicated than the questions answered by science and medicine.


Dr Ang, the medical director of Parkway Cancer Centre, has been treating cancer patients for 23 years. In 1996, he was awarded Singapore's National Science Award for his outstanding contributions to medical research

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