Should Ebola Vaccines Be One Shot Or Two? The Answer Could Determine Success Of Mass Immunization

A baby is prepared for a vaccination during a routine doctor's visit at the Kuntorloh Community Health Centre in the outskirts of Freetown on November 14, 2014. Ebola-hit Sierra Leone faces social and economic disaster as gains made since the country's ruinous civil war are wiped out by the epidemic, according to a major study. Damage to most sectors of the economy will see growth shrink from 20.1 percent last year to just five percent in 2014, the finance ministry and the United Nations Development Programme (UNDP) found. AFP PHOTO/ FRANCISCO LEONG        (Photo credit should read FRANCISCO LEONG/AFP/Getty Images)
A baby is prepared for a vaccination during a routine doctor's visit at the Kuntorloh Community Health Centre in the outskirts of Freetown on November 14, 2014. Ebola-hit Sierra Leone faces social and economic disaster as gains made since the country's ruinous civil war are wiped out by the epidemic, according to a major study. Damage to most sectors of the economy will see growth shrink from 20.1 percent last year to just five percent in 2014, the finance ministry and the United Nations Development Programme (UNDP) found. AFP PHOTO/ FRANCISCO LEONG (Photo credit should read FRANCISCO LEONG/AFP/Getty Images)

By Ben Hirschler and Kate Kelland

LONDON, Dec 11 (Reuters) - Scientists racing to develop vaccines against Ebola are trying to determine whether they can best fight the disease with a single injection or with two, a calculation that could determine how quickly and effectively a program can be rolled out.

Administering two vaccines, one after the other, would almost certainly give far greater protection than a single shot against a deadly virus that has killed more than 6,000 people in West Africa this year.

But it would also make mass immunisations far more complicated in the worst-affected countries of Guinea, Liberia and Sierra Leone, where weak health systems have all but collapsed under the weight of the epidemic.

With the epidemic growing exponentially through much of 2014, the initial focus was on developing a single shot that could be tested and deployed as fast as possible.

Now, however, with disease transmission rates tailing off markedly in Liberia, there is more debate about a double vaccine program that would provide greater protection, even if it might take longer and be harder to implement.

"There is now more and more talk about what can we do to prolong vaccine protection," said Ripley Ballou, head of Ebola research at GlaxoSmithKline, which has one of the leading vaccine candidates.

He still hopes a single-dose vaccine will be of use in the current outbreak, but also sees a need to evaluate the "prime-boost" approach of giving a first shot to stimulate the immune system, followed by a second booster a few weeks later.

Health officials in London and Washington, as well as non-profit groups like the Wellcome Trust that are also helping fund clinical trials, are liaising closely on the best way forward.

"We're trying to decide where it is best to put the money," said one senior government adviser.

A big Liberia trial, involving up to 30,000 participants, will test single shots of GSK's vaccine, a rival one from NewLink and Merck, and a placebo.

Although the Ebola slowdown in Liberia is clearly good news, it means the trial may not see enough new cases of disease to demonstrate the benefit of vaccination.

PRODUCTION CAPACITY

Other studies are starting to analyze the prime-boost approach. Johnson & Johnson expects to start testing its experimental shot with a booster developed by Denmark's Bavarian Nordic "very soon" and its chief scientific officer, Paul Stoffels, is convinced this is the right strategy.

"It is cumbersome, because you need two vaccines, but it is clear that you will get the best protection, both short and long term, from a prime-boost," he said.

A prime-boost vaccine will be more difficult to make in large quantities, since the booster component from Bavarian needs to be grown in chicken eggs, limiting supply. But past experience suggests it should pack more punch.

Tests of similar two-pronged vaccines in other diseases suggest the booster component can increase immune responses around 30-fold for the production of antibodies and up to 10-fold for the body's own disease-fighting T-cells - two of the key elements of the ability to fight off infection - said Adrian Hill, a vaccine expert at Oxford University's Jenner Institute.

That extra protection may be needed in West Africa, where infection with malaria could also depress people's immune systems, limiting the effectiveness of immunization.

In the end, the wide program of vaccine trials scheduled for the first half of 2015 may yield a variety of options, with some experts suggesting prime-boost may be particularly suited for healthcare workers facing regular high exposure and single shots the preferred choice for rapid containment of local cases.

So far, the only human data on how well Ebola vaccines might work comes from the United States and Europe, with GSK's shot proving safe and showing some efficacy, although not comprehensive protection. NewLink's experimental shot had no serious side effects but caused some mild fever.

With the epidemic still raging, tests are likely to try out combinations of vaccines in an opportunistic way. While their impact may not become clear until later next year, the lessons learned will still be valuable in responding to the next, inevitable, Ebola outbreak.

"This disease is going to be endemic in West Africa," said GSK's Ballou. "It's important for those countries either to have routine vaccination or a stockpile option." (Editing by Peter Graff)

1
Ebola is highly infectious and even being in the same room as someone with the disease can put you at risk
ASSOCIATED PRESS
Not as far as we know. Ebola isn't contagious until symptoms begin, and it spreads through direct contact with the bodily fluids of patients. It is not, from what we know of the science so far, an airborne virus. So contact with the patient's sweat, blood, vomit, feces or semen could cause infection, and the body remains infectious after death. Much of the spread in west Africa has been attributed to the initial distrust of medical staff, leaving many to be treated at home by loved ones, poorly equipped medics catching the disease from patients, and the traditional burial rites involving manually washing of the dead body. From what we know already, you can't catch it from the air, you can't catch it from food, you can't catch it from water.
2
Cancelling all flights from west Africa would stop the spread of Ebola
ASSOCIATED PRESS
This actually has pretty serious implications. British Airways suspended its four-times-weekly flights to Liberia and Sierra Leone until the end of March, the only direct flight to the region from the UK. In practice, anyone can just change planes somewhere else and get to Britain from Europe, north Africa, or the Middle East. And aid agencies say that flight cancellations are hampering efforts to get the disease under control, they rely on commercial flights to get to the infected regions. Liberia's information minister, Lewis Brown, told the Telegraph this week that BA was putting more people in danger. "We need as many airlines coming in to this region as possible, because the cost of bringing in supplies and aid workers is becoming prohibitive," he told the Telegraph. "There just aren't enough seats on the planes. I can understand BA's initial reaction back in August, but they must remember this is a global fight now, not just a west African one, and we can't just be shut out." Christopher Stokes, director of MSF in Brussels, agreed: “Airlines have shut down many flights and the unintended consequence has been to slow and hamper the relief effort, paradoxically increasing the risk of this epidemic spreading across countries in west Africa first, then potentially elsewhere. We have to stop Ebola at source and this means we have to be able to go there.”
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Temperature screening at airports is an effective way to stop those who have the disease from travelling
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The screening process is pretty porous, especially when individuals want to subvert it. Wake up on the morning of your flight, feel a bit hot, and you definitely don't want to be sent to an isolation booth for days and have to miss your flight. Take an ibuprofen and you can lower your temperature enough to get past the scanners. And if you suspect you have Ebola, you might be desperate to leave, seeing how much better the treatment success has been in western nations. And experts have warned that you cannot expect people to be honest about who they have had contact with. Thomas Eric Duncan, the Ebola victim who died in Texas, told officials he had not been in contact with anyone with the disease, but had in fact visited someone in the late stages of the virus, though he said he believed it was malaria. The extra screening that the US implemented since his death probably wouldn't have singled out Duncan when he arrived from hard-hit Liberia last month, because he had no symptoms while travelling.
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Border staff should stop people coming in to the country who are at risk
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They're not doctors, and it's a monumental task to train 23,500 people who work for the UK Border Agency how to correctly diagnose a complex disease, and spot it in the millions of people who come through British transport hubs. Public Health England has provided UK Border Force with advice on the assessment of an unwell patient on entry to UK, but they can't be expected to check everyone.
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Screening at British airports should be implemented to stop unwell people coming in from affected areas
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As mentioned before, the UK, especially London, is a major transport hub. Unlike the US, most of those coming from west Africa will have crossed through Europe, so infected people could be coming from practically anywhere, not just flights directly from those countries. This would require the UK to screen every returning traveller, as people could return to the UK from an affected country through any port of entry. This would be huge numbers of low risk people, at vast, vast expense.