The findings of a new study published in Cancer Prevention Research, a journal of the American Association for Cancer Research, suggest that one dose of the human papillomavirus (HPV) vaccine may provide sufficient protection against cervical cancer. This offers the possibility of simplifying the administration of the vaccine, which currently entails the need for three doses spread over a twelve month period.
The research discovered that women vaccinated with one dose of a the HPV vaccine had antibodies against the viruses that remained stable in their blood for four years, suggesting that a single dose of vaccine may be sufficient to generate long-term immune responses and protection against new HPV infections, and ultimately cervical cancer.
Dr Mahboobeh Safaeian, an investigator in the Division of Cancer Epidemiology and Genetics at the National Cancer Institute in Bethesda, USA said:
"We wanted to evaluate whether two doses, or even one dose, of the HPV 16/18 L1 VLP vaccine could induce a robust and sustainable response by the immune system." “We found that both HPV 16 and HPV 18 antibody levels in women who received one dose remained stable four years after vaccination. Our findings challenge previous dogma that protein subunit vaccines require multiple doses to generate long-lived responses."
The researchers looked for the presence of an immune response to the vaccine (measured by antibody levels) in blood samples drawn from 78, 192, and 120 women who received one, two, and three doses of the vaccine, respectively, and compared the results with data from 113 women who did not receive vaccination but had antibodies against the viruses in their blood because they were infected with HPV in the past.
They found that 100 per cent of the women in all three groups had antibodies against HPV 16 and 18 in their blood for up to four years. Antibody levels were comparable for women receiving two doses six months apart and those receiving the full three doses.
The researchers also found that while antibody levels among women who received one dose were lower than among those who received the full three doses, the levels appeared stable, suggesting that these are lasting responses. In addition, the levels of antibodies in women from the one- and two-dose groups were five to 24 times higher than the levels of antibodies in women did not receive vaccination, but had prior HPV infection.
"Our findings suggest promise for simplified vaccine administration schedules that might be cheaper, simpler, and more likely to be implemented around the world," said Safaeian. "Vaccination with two doses, or even one dose, could simplify the logistics and reduce the cost of vaccination, which could be especially important in the developing world, where more than 85 per cent of cervical cancers occur, and where cervical cancer is one of the most common causes of cancer related deaths."