Tuesday, March 31, 2009

STI: Safety's the key issue - not sex

March 28, 2009


Safety's the key issue - not sex

By Andy Ho


THERE is now an anti-cancer vaccine called Cervarix. Its maker, GlaxoSmithKline, has just dropped its price by a third. It now costs $450 for three required shots.


The vaccine works against four strains of the human papillomavirus (HPV) - two that cause cervical cancer and two genital warts. It also prevents some vaginal, vulvar, anal and throat cancers.


Although it is presently recommended for females aged 10 to 25 only, Nobel laureate Harald zur Hausen, who won the prize last year precisely for discovering the HPV-cervical cancer link, urges that boys also be vaccinated.


This is because HPV raises the risk of throat cancer 12-fold. Mathematical models show that vaccinating only females would merely be 60 to 75 per cent as effective at reducing HPV in females overall compared to vaccinating both sexes.


At any rate, only 1 per cent of women in the recommended age group have received the pricey shots. Cost aside, the media reported last week that 1,500 females in Britain developed paralysis, convulsion, and sight problems after Cervarix. In February, after two girls developed similar problems in Spain, the authorities there temporarily halted the use of Gardasil, an identical vaccine made by Merck.


According to an Australian study published in September last year in the Canadian Medical Association Journal, the rate of anaphylaxis - a serious total body allergic reaction that can lead to death - following Gardasil was significantly higher than other childhood vaccines.


Gardasil's overall rate of anaphylaxis is 2.6 per 100,000 doses administered. By contrast, those for the meningococcal C, MMR (measles-mumps-rubella), hepatitis B, and measles-rubella vaccines are 0.4, 0.41, 0.78 and 1 per 100,000 doses administered, respectively.


The researchers from Australia's National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases suggested that its higher rates might be caused by yeast proteins present in the vaccine or a stabiliser called polysorbate 80. Or, the attenuated HPV proteins themselves might be the cause, they postulated. However, their findings 'should not curtail' HPV vaccination for the population at large, they opined.


Largely concurring with this conclusion, the US Food and Drug Administration and the Centres for Disease Control and Prevention announced last July that they 'continue to find Gardasil...safe and effective (whose) benefits continue to outweigh the risks'. Most advocates argue that many of the adverse effects noted are probably phenomena occurring naturally in the population, so they would have occurred in the patients involved had they not been vaccinated anyway. That is, the vaccine was not the cause at all.


However, noting that activists and manufacturers have put pressure on policymakers worldwide to adopt the vaccine, especially in childhood vaccination programmes, an editorial in the August 2008 issue of the New England Journal of Medicine cautioned that there was 'good reason to be cautious about introducing large-scale (HPV) vaccination programmes'.


Many questions remain. For one, we don't know how long the immunity the drug confers will last. Studies suggest that the three-dose series will not likely prevent cancer indefinitely. Thus boosters will be needed and costs will rise further. We also don't know if the vaccine will affect natural immunity against HPV. After all, in 80 per cent of HPV infections, the body's natural defences clear them out within two years.


Some 40 of the 100 HPV types that exist cause all known cases of cervical cancer. However, the vaccine covers only types 16 and 18, because the duo are responsible for 70 per cent of the cases. Yet other types are becoming increasingly responsible for some pre-cancerous cervical problems.


Then there is the worry that the vaccine may lull some women into the wrong idea that pap smears, the mainstay in preventing cervical cancer, are no longer important. In fact, not all vaccinated women are absolutely protected from the cancer. For all these reasons - and because questions about its safety remain - there are some who argue against the vaccine.


Then there are the moralists who feel the vaccine could promote premarital sex and encourage promiscuity among adolescents. Some fear that vaccinating young girls against a disease that can only be transmitted sexually might send them the wrong message. Adolescents may read it as tacit approval for sexual activity. They may also develop a false sense of security, thinking that they are protected against other sexually transmitted diseases too.


Feminists argue, however, that this notion of a vaccine fomenting promiscuity is merely the expression of a misplaced fear of female sexuality. To deny girls protection against a sexually transmitted, cancer-causing virus is to imply that boys deserve to be protected from female sexuality more than girls deserve to be protected from cervical cancer. Girls are not worth less than boys, they assert.


Perhaps if both sides kept in view whom it is that we want protected - our daughters, sisters and wives - then we might not be inclined to construe the issue in terms of whether or not we are promoting irresponsible sex. Rather, it is about protecting our children's health - once we are sure the vaccine is truly safe.




Daedalus (meaning 'cunning worker' in Greek) was the man who built wings so he and his son Icarus could fly. As Icarus flew too close to the sun, his wings melted and he crashed to earth. Daedalus is a weekly column on the triumphs and challenges of science and technology.

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