EFFICACY OF THE QUADRIVALENT HPV VACCINE IN CERVICAL CANCER PREVENTION STRATEGY IN THE GAMBIA.
Persistent infection with high risk Human Papillomavirus (HR HPV) genotype causes 80% of cervical cancers. HR HPV 16 and 18 are responsible for 70% of cervical cancers, worldwide. Three prophylactic HPV vaccines have been developed to prevent HPV infections. In the Gambia, cervical cancer is the most frequent diagnosed cancer representing approximately 30% of all female cancers. The quadrivalent HPV vaccine, which targets genotypes 16, 18, 6 and 11 was recently piloted in the West Coast Region where majority of cervical cancer cases were reported. In order to evaluate the potential efficacy of the quadrivalent vaccine, this study assessed regional genotype distribution to ensure the HPV vaccine prevention strategy would be effective.
232 endocervical samples were collected from women age 20 - 49 years old residing in Banjul and West Coast Region. DNA was isolated using the QIAamp DNA Mini Kit (Qiagen). HPV detection was carried out by PCR amplification using primer sets PGMY09/11, which target the (L1) Major capsid gene of the virus. Genotyping was performed by Sanger sequencing technique.
Eight different HR HPV genotypes were identified. HPV 52 (28.6%) was the most prevalent genotype, followed by 58 and 51(both 14.2%). HPV 16 (7.1%) was the seventh most common genotype identified and HPV 18 was not detected. HR HPV distribution was higher in the 26-30 age group. HPV 61 was the most common low risk genotype isolated. Sequence analysis showed all HR genotypes detected were not homologous to African isolates but isolates originated from America, Europe and Asia.
The success of a cervical cancer vaccine prevention strategy should consider the dominant circulating HR HPV type. In the Gambia, the vaccine currently available may be of limited use.