Cervical cancer vaccine offers distant hope

Two new vaccines that protect women against cervical cancer could save thousands of lives in sub-Saharan Africa, where most cases of cervical cancer go undetected until they are too far advanced to treat. The vaccines hold particular promise for women who contract HIV and become more susceptible to the human papilloma virus (HPV), the sexually transmitted infection that can cause cervical cancer.

About half a million women worldwide are diagnosed with cervical cancer every year, but effective screening programmes in the developed world have substantially reduced mortality. Most of the 250,000 deaths caused by the disease now occur in developing countries, which lack the infrastructure and resources to implement routine screening.

The HIV/AIDS epidemic in sub-Saharan Africa may have contributed to the high number of cervical cancer deaths: women infected with HIV are thought to be three to five times more likely to develop cervical lesions that can become cancerous.

Prof Lynn Denny, who heads the Gynaecological Oncology unit at the University of Cape Town, believes an HPV vaccine holds "huge" promise for southern Africa.

"If made widely available, it has the potential to reduce cervical cancer by at least 70 percent - probably more - and is going to be much more implementable than screening, but it is currently too expensive and I reckon it will take another 10 years before the vaccine will be introduced into developing countries."

One of the vaccines given to pre-adolescent girls in three injections over six months is already available in the United States and the United Kingdom, but its current cost ($360) puts it beyond the reach of most developing countries.

It is also not yet known how effective it would be for women in Africa, particularly those who are HIV-positive. The vaccine protects against two HPVs that most commonly cause cervical cancer in North America and Europe, but these types are slightly less common in sub-Saharan Africa and may be even less common in women with HIV.

Screening barriers

In Europe and the United States, women are encouraged to go for a pap smear, in which a sample of cervical cells is collected and checked for abnormalities, once every two or three years.

''it has the potential to reduce cervical cancer by at least 70 percent - probably more - and is going to be much more implementable than screening, but it is currently too expensive ...''

In South Africa, where cervical cancer accounts for about 25 percent of cancer deaths among black women, there is no formal pap smear programme and women seeking pap smears in the public health sector are only eligible for one every 10 years after the age of 30. A lack of public education about cervical cancer means that many women never request them.

In the context of an over-burdened under-resourced public health sector, partly as a result of South Africa's HIV/AIDS epidemic, the barriers to implementing more regular screening are considerable.

Pap smears are expensive, costing about R65 (US$9) each, and any abnormality detected requires referrals and follow-up which, according to Prof Helen Rees, executive director of the Reproductive Health and HIV Research Unit at the University of Witwatersrand, "don't always happen when services are overstretched".

"It's very challenging to roll out, even in urban centres," she said, because women often do not come for repeat visits, or go to other centres they may be referred to, creating a growing caseload that needs to be followed up.

Through a study of 7,000 women in Khayelitsha, Cape Town's largest township, Denny piloted a cheap, low-tech alternative to pap smears that nurses at primary healthcare clinics can use to screen and treat a woman in one visit.

Simply applying acetic acid to the cervix causes abnormalities to show up white. These areas can then be treated by freezing them with liquid nitrogen. Not all abnormalities are cancerous and there is a tendancy to over-treat, but when the alternative is no treatment at all and the HPV vaccine is still several years away, the method could save lives.

Lack of provisions for positive women

Despite their increased risk, HIV positive women lacked any special cervical screening provisions until recently. The newly adopted National Strategic Plan for HIV and AIDS recommends a pap smear for women about to begin antiretroviral treatment. "Ideally, it [the pap smear] should be when they're diagnosed, but our health service is really buckling," Rees told IRIN/PlusNews. "So if we can at least get one in, that will help."

''With sufficient political will, an HPV vaccination programme targeting girls aged 10 to 12 would be feasible''- Prof Helen Rees

Denny would like to see HIV positive women getting additional pap smears every two or three years, but noted the need for more research into the progression of cervical disease in HIV infected women.

From a study now in its fifth year in Nyanga, another Cape Town township, Denny and her colleagues found that HIV-positive women had a higher prevalence of HPV infection than HIV-negative women, and were more likely to have multiple high-risk types of HPVs. The two types of HPV that the new vaccines are effective against were not the ones most commonly contracted by women included in the study.

Prototype for HIV vaccination

Findings from studies looking at what an HPV vaccine could mean to older women infected with HPV or even HIV are still several years away, but Rees was convinced that with sufficient political will, an HPV vaccination programme targeting girls aged 10 to 12 would be feasible.

PATH, a non-profit global health organisation, is running studies in four countries, including Uganda, to look at how best to deliver an HPV vaccine to girls before they become sexually active, how much it would cost and what some of the social and cultural barriers might be.

"The big stumbling block at the moment is the price, but both companies [each producing a vaccine] have indicated they're willing to have discussions about tiered pricing. We just need to show with cost effectiveness studies that it would be worthwhile," she said.

Rees believes that solving some of these issues will have value even beyond the introduction of an HPV vaccine.

"The recommendation is for pre-adolescant girls [to receive the HPV vaccine] and should we, in the future, acquire an HIV vaccine, that is also the age we'd want to target. So what we're looking at is a prototype, because there are no vaccine programmes targeting that age group right now," she said.

Incorporating the delivery of the three HPV shots into a broader sexual health programme for young people could be another benefit, she added.