Daniela Ginta, MSc
Cancer - it's a formidable foe. Finding a cure for one of the most dreaded diseases is still proving elusive, but prevention is now gaining attention with the advent of cancer vaccines. But are vaccines all their manufacturers promise them to be?
Cancer—it’s a formidable foe. Finding a cure for one of the most dreaded diseases is still proving elusive, but prevention is now gaining attention with the advent of cancer vaccines. But are vaccines all their manufacturers promise them to be?
Many cancers can be prevented, but prevention is complicated by the fact that cancer has many causes–both genetic and environmental. Cancer is not caused exclusively by an unhealthy lifestyle. Problems associated with a certain genetic makeup, which sometimes cannot be fixed by the body’s repairing mechanisms, can trigger tumour formation. However, cancers caused by environmental factors, such as virus infection or unhealthy lifestyle, should be preventable.
Vaccines targeting certain cancer-causing viruses are emerging as a strong weapon against cancer. There are two types of cancer vaccines: preventive (or prophylactic) and therapeutic. Prophylactic vaccines are administered to healthy individuals and help to prevent infection from certain cancer-causing viruses, such as hepatitis B and human papillomavirus (HPV). Therapeutic vaccines, administered to cancer patients, work in conjunction with specific cancer treatments.
Cervical Cancer–a Thing of the Past?
One such prophylactic vaccine has been developed to protect against cervical cancer. In Canada it is estimated that approximately 400 women die annually from this kind of cancer, the major cause of which is believed to be persistent HPV infection. It is estimated that over 99 percent of cervical cancers are caused by HPV. Four of the common types of HPV (types 6, 11, 16, and 18) can be prevented through vaccination.
According to the Public Health Agency, an HPV vaccine was approved in July 2006 for use in Canada by females between nine and 26 years of age. The National Advisory Committee on Immunization, however, has yet to determine recommendations for use.
Two pharmaceutical companies have developed vaccines against HPV 16 and 18, the two types of viruses that together cause approximately 75 percent of the cervical cancer cases. One type of vaccine also protects against HPV 6 and 11, the two strains responsible for almost 90 percent of the genital warts cases.
For maximum efficiency the vaccine must be administered to young girls before they start their sexual life. Booster shots are needed after a certain time. “The longest study has a follow-up of just over five years and protection seems to hold steady for this long. It is quite possible that protection will last for at least 10 years,” says Eduardo Franco, PhD, professor of epidemiology and oncology and director of the Division for Cancer Epidemiology at McGill University.
There is also an experimental HPV vaccine being tested for men. However, Dr. Franco says, “The major goal should be to make the HPV vaccine available for young women in developing countries, where cervical cancer affects approximately 225,000 women annually.”
Cancer Vaccines–the Panacea?
Vaccines that prevent or treat cancers could be the answer to one of the most difficult health threats that people face, but does the cancer vaccine have drawbacks?
An earlier version of the HPV vaccine was effective at preventing infection with HPV 16, but the antibody level decreased during ovulation, making women more susceptible to infection.
In Dr. Franco’s opinion, however, there should be no reason for concern with the new HPV vaccines. “Women in these vaccine trials have experienced over 60 menstrual cycles and protection continues to be 100 percent.”
Dr. Franco does caution that while the vaccine ensures protection, women should still be screened regularly for abnormal cervical cells by having annual Pap tests. The vaccine, after all, protects against only two of the HPV types, responsible for approximately 75 percent of all cervical cancers.
Conservative groups are putting the HPV vaccine into a different light. Some medical professionals and parents feel that immunization of teenage girls against infection with HPV may condone teen sex. They feel that teenagers might believe that the vaccine makes sex safe. This, of course, is not true; the vaccine only protects against certain strains of HPV but does not offer protection against other sexually transmitted diseases.
Questions about HPV vaccine’s efficacy are raised by Joseph Mercola, MD, who argues that there is still no clear correlation between HPV infection and cervical cancer. Cervical cancer, he claims, might also be caused by carcinogens. He believes most women are able to fend off HPV infection on their own, without any vaccine.
He also adds that even if HPV indeed causes cervical cancer, there are approximately 30 strains of HPV that are possible causes of cancer. Therefore, since the vaccine protects only against two of the most dangerous strains, it is still possible for a vaccinated woman to become infected with another of the cancer-causing HPV strains.
The Debate Continues
As with most vaccines, the debate will go on. While some argue that cancer vaccines offer the best protection, there are also strong opponents to the use of yet another vaccine. Instead, they say, make use of natural ways to strengthen the immune system, enabling it to fight infection and avoid cancer formation.
Natural Cancer-Fighting Strategies
Cervical cancer risk can be lowered by increasing consumption of foods rich in beta carotene and vitamin C and by avoiding oral contraceptives, which are associated with a higher risk of cervical cancer.
Avoid other risk factors including a high number of sexual partners, starting sexual life during early teenage years, and smoking, since tobacco smoke is a known carcinogen.
Maintain emotional balance and a healthy lifestyle that includes regular exercise and plenty of sleep to help prevent cancer formation naturally.