ARTICLE - CHOLERA VACCINES

WOULD CHOLERA VACCINES HAVE HELPED IN HAITI?
(Nature.com)

Three leading researchers today called for the United States to create a national stockpile of cholera vaccines that could be quickly deployed worldwide whenever an outbreak occured.

In an opinion article published online by the New England Journal of Medicine the researchers – Matthew Waldor, a cholera researcher at Harvard Medical School in Boston, Peter Hotez president of the Sabin Vaccine Institute in Washington DC, and John Clemens, head of the International Vaccine Institute in Seoul – argue that vaccination could have an enormous impact in controlling cholera outbreaks, such as the current one raging in Haiti, and also serve US foreign policy interests, through "vaccine diplomacy."

The question of whether vaccine could have helped in Haiti - or help in future outbreaks - is controverial, however. It's one issue that I've addressed in a long analysis on the Haiti outbreak published in this week's issue of Nature. I've excerpted the relevant part in full below, which describes how those working in the field remain highly sceptical of the utility of cholera vaccine in an outbreak situation.

See below the fold for the full excerpt:

"When the cholera outbreak started in Haiti, health agencies briefly contemplated using vaccines to try to curb it. But they abandoned the idea once it became clear that the available global production was completely insufficient for an effective vaccination campaign — only a few hundred thousand doses would have been available, and even these would have taken weeks to manufacture, whereas millions of doses were needed.

Only one cholera vaccine — Dukoral — is approved by the World Health Organization (WHO). Made by the small Dutch company Crucell, based in Leiden, it is aimed at people travelling to cholera-endemic areas, and as such is too expensive to be widely deployed in the developing world. A second vaccine called Shanchol, already licensed in India, is currently going through the WHO’s approval process. Developed by the International Vaccine Institute in Seoul, with support from the Bill & Melinda Gates Foundation, the vaccine is produced by Shantha in Hyderabad, India, and should cost less than US$1 a dose.

Even if sufficient Dukoral or Shanchol had been available at the start of the Haitian outbreak, it might have had little impact. Two doses of the vaccines have to be given a fortnight apart, with protective immunity taking another week to form. Mounting a large vaccination campaign also causes inevitable delays. So it is by no means clear that vaccination would have made any major dent in the spread of the disease (such delays have been experienced in past reactive vaccination campaign during meningitis outbreaks in Africa -- see my recent article on this here).

The logistics would have been daunting, says Claire-Lise Chaignat, coordinator of the WHO’s Global Task Force on Cholera Control. Just vaccinating the 2 million people in the Haitian capital Port-au-Prince would have required rapid deployment of some 4 million vaccine doses. That’s a huge logistical challenge in any situation, but in the dire conditions Haiti now finds itself in it would be “almost impossible”, she says.

Had sufficient vaccine been available, Jon Andrus, deputy director of the Pan American Health Organization, says that he would have considered trying vaccination in case it had a positive impact. Pre-emptive vaccination of people in the neighbouring Dominican Republic could also have made sense, he says.

In the longer term, vaccination for cholera deserves further study, says Robert Quick, an epidemiologist at the Enteric Diseases Epidemiology Branch of the Centers for Disease Control and Prevention in Atlanta, Georgia. If a longer-lasting and highly efficient single-dose vaccine could be developed it might make a significant impact on outbreaks such as Haiti’s. A single-dose vaccine called Orochol has been developed, but its manufacturer, the Swiss company Berna Biotech (acquired by Crucell, based in Berne, in 2006), stopped making it in 2004 after switching its limited production facilities to make another vaccine.

But Quick emphasizes that a single-dose vaccine would not be a panacea, and stark choices would remain. Mounting a vaccine campaign during an outbreak takes away scarce resources and staff, he argues. “Do you want staff treating people, or vaccinating?” he asks. “The first priority is saving lives.”