Merck's Gardasil looks effective in two-shot regimen

Merck's ($MRK) Gardasil and GlaxoSmithKline's ($GSK) Cervarix have racked up billions of dollars in sales, but low vaccination rates have constrained both earnings and health benefits. Vaccine skepticism, cost and the challenge of administering a three-dose regimen have held back uptake.

New research suggests that problems associated with the three-dose regimen could be limited by cutting back to two shots. A Canadian Health Ministry-backed study published in the Journal of the American Medical Association (JAMA) found that two doses of Gardasil could be as effective as the current three-shot system. Girls aged 9 to 13 who received two shots had comparable antigen levels to those of older women previously given the three-dose regimen. Research is now needed to monitor whether antigen levels fade when just two shots are given. If so, a booster would be needed.

The outcome of the follow-ups could have a bearing on how countries administer Merck's human papillomavirus vaccine. Talking to Bloomberg, lead study author Simon Dobson said: "The public health question is, is there enough information in this study to say that a two-dose schedule for young girls is all right. The answer is not quite yet." While a switch to a two-dose regimen would reduce the number of shots Merck and GSK sell per patient, it could expand access overall.

In an accompanying editorial, pediatrics professor Jessica Kahn wrote that HPV vaccine uptake is restricted by the logistical complexities of the three-dose regimen. Even in Australia--which is ahead of most countries with HPV vaccinations--the number of kids receiving the final dose drops off by 12%. The U.S. found a similar problem in its national immunization survey, but it also suffers from higher initial opt-out rates. Both would increase regimen completion rates if a two-shot program was adopted, while the lower costs and complexity would make HPV vaccines more viable anywhere cash and infrastructure is limited.

- here's the Bloomberg article
- check out the JAMA paper
- read the JAMA editorial (sub. req.)