The first wave of the COVID-19 pandemic may be waning. For vaccine developers, that could be a problem.
Scientists in Europe and the United States say the relative success
of draconian lockdown and social distancing policies in some areas and
countries means virus transmission rates may be at such low levels that
there is not enough disease circulating to truly test potential
vaccines.
They may need to look further afield, to pandemic hotspots in Africa and Latin America, to get convincing results.
“Ironically, if we’re really successful using public health measures
to stamp out the hot spots of viral infection, it will be harder to test
the vaccine,” said Francis Collins, director of the National Institutes
of Health in the United States.
A vaccine is seen as essential to ending a pandemic that has killed
nearly 370,000 people and infected more than 6 million so far, with
world leaders looking at inoculation as the only real way to restart
their stalled economies.
But running large-scale clinical trials of potential vaccines against
a completely new disease at speed is complex, scientists say. Showing
efficacy in those trials during a fluctuating pandemic adds extra
difficulty – and doing so when outbreaks are waning makes it harder
still.
“For this to work, people need to have a risk of infection in the
community. If the virus has been temporarily cleared out, then the
exercise is futile,” said Ayfer Ali, an expert in drug repurposing at
Britain’s Warwick Business School.
“The solution is to move to areas where the infection is being spread
widely in the community – that would be countries like Brazil and
Mexico at the moment.”
Vaccine trials work by randomly dividing people into a treatment
group and a control group, with the treatment group getting the
experimental trial vaccine and the control group getting a placebo.
All participants go back into the community where the disease is
circulating, and subsequent rates of infection are compared. The hope is
that infections within the control group will be higher, showing the
trial vaccine is protecting the other group.
With COVID-19 epidemics in Britain, mainland Europe and the United
States coming down from their peak and transmission rates of the
coronavirus dropping, a key task for scientists is to chase fluctuating
outbreaks and seek volunteers in sections of populations or in countries
where the disease is still rife.
A similar problem emerged when scientists were seeking to test
potential new vaccines against Ebola during the vast 2014 outbreak in
West Africa. Then, drugmakers were forced to drastically scale back
plans for large trials because their vaccines were only test-ready late
in the epidemic when case numbers were dwindling.
reut.rs/36OmkVu
For an interactive graphic tracking the global spread, open
tmsnrt.rs/3aIRuz7 in an external browser
LOOKING ABROAD
Among the first COVID-19 vaccines to move into phase two, or mid-stage, trials is one from the U.S. biotech company Moderna (
MRNA.O) and another being developed by scientists at Oxford University supported by AstraZeneca (
AZN.L). The United States in July is planning to launch vast efficacy trials of 20,000 to 30,000 volunteers per vaccine.
Collins said U.S. health officials will tap government and industry
clinical trial networks in the United States first and use mapping to
detect where the virus is most active. They will also consider looking
abroad if domestic disease rates fall too far, he said.
The U.S. government has experience in Africa of testing vaccines against HIV, malaria and tuberculosis.
“Africa is now beginning to experience lots of cases of COVID-19. We
might very well want to run part of the trial there, where we know we
can collect the data effectively,” said Collins.
Adrian Hill, director of the Jenner Institute at Britain’s Oxford
University which has teamed up with AstraZeneca, started mid-stage
trials last month which he said would aim to recruit around 10,000
people in Britain.
He told Reuters that with COVID-19 disease transmission rates
dropping in the UK there is a possibility that the trial would have to
be halted if they didn’t have enough infections to yield a result.
“That would be disappointing, and at the moment it’s unlikely, but it’s certainly a possibility,” Hill said.
CHALLENGE TRIALS
Underscoring the level of concern in the industry, AstraZeneca’s
chief executive Pascal Soriot said his researchers were even
contemplating running so-called “challenge” trials – where participants
would be given the experimental vaccine and then deliberately infected
with COVID-19 to see if it worked. Such trials are rare, high risk and
hard to get ethical approval for.
As a more practical and swifter option, Soriot and others are looking
to Brazil and other countries in South America, as well as parts of
Africa where COVID-19 outbreaks are still growing and peaking, as ripe
drug and vaccine testing grounds.
Difficulty recruiting candidates for mid-stage vaccine trials in
countries where the COVID-19 pandemic is on the wane may be foreshadowed
by the experience of doctors seeking infected cases for the World
Health Organization’s multi-country Solidarity trial of potential
treatments for the disease – including the generic drug
hydroxychloroquine and Gilead’s (
GILD.O) remdesivir.
In the Swiss portion of that trial, for instance, it took three weeks
to get all of the ethical and regulatory approvals from authorities,
and another week to get all the drugs, said Oriol Manuel, an infectious
disease expert and national coordinator of the Solidarity study in
Switzerland.
“We were able to enroll some patients in (one trial centre in)
Lausanne,” Manuel said. “But when all centres were ready, the cases were
fortunately disappearing.”
https://www.reuters.com/article/us-health-coronavirus-vaccine-hunt-insig/scientists-hunt-pandemic-hotspots-in-race-to-test-vaccines-idUSKBN2381DT
