181 CMAAO
CORONA FACTS and MYTH Human Challenge
Dr K
Aggarwal
President
CMAAO
With inputs
from Dr Monica Vasudev
1047: Human Challenge Trials for COVID-19 Vaccine and
the Risk?
Human
challenge trials for the COVID-19 vaccine —volunteering to be given an unproven
vaccine, then being exposed to the virus on purpose instead of waiting to be
exposed and for infection to occur naturally in the community.
The goal is
to speed vaccine development. More than 32,000 people from the United States
and 139 other countries have already signed up with an online registry, 1Day
Sooner.
The trials
could effectively deliver a vaccine and end the pandemic more quickly, but the
unknowns about this novel coronavirus, the lack of an effective treatment for
COVID-19, and the accelerated pace of the research give pause, because the
extra risk could come at a high cost: the health, or potentially the life, of
the volunteers.
These trials
can be faster than conventional field trials, partly because fewer participants
must be exposed to provide early estimates of efficacy and safety; if one
vaccine doesn't work, researchers can move on to other candidates. In challenge
trials, volunteers receive the vaccine candidate or a placebo, just as
participants in traditional trials do. After waiting a period for the vaccine
to take effect, the volunteers are exposed to the virus.
Whereas
traditional vaccine trials may enroll 30,000 participants in phase 3 studies
and have results in 6 months, challenge trials may need only about 150
participants and have results in 6 weeks. In addition, the studies can compare
multiple vaccine candidates at once; the most promising are selected to move on
to larger studies.
Can a
volunteer really give informed consent when there are so many unknowns about
COVID-19? Clinicians say they would communicate the pros and cons should one of
their patients ask about joining up.
In the past
50 years, the WHO says, ''challenge studies have been performed safely in tens
of thousands of consenting adult volunteers under the oversight of research
ethics committees." The studies have helped to speed development of
vaccines against cholera and typhoid and to evaluate immune protection against
influenza.
Shaving even
1 day off vaccine development time could save 7120 lives, according to
estimates by experts.
Reducing
development time by 3 months would save more than a half million lives,
estimated, assuming that one sixth of the world would acquire COVID-19 annually
and that a vaccine would prevent 0.2% of those people from dying.
Study
participants may be high-risk individuals who volunteer because they believe
that these first vaccine attempts could prevent them from contracting COVID-19,
a belief of the "prevention misconception."
Guidance On
Glycemia in Dexamethasone-Treated COVID-19
New guidance
from the UK National Diabetes COVID-19 Response Group
Triple
insult of dexamethasone-induced impaired glucose metabolism, COVID-19-induced
insulin resistance, and COVID-19 impaired insulin production.
August 2 in
Diabetic Medicine
Randomised
Evaluation of COVID-19 Therapy (RECOVERY) trial, showed that dexamethasone
reduced deaths in patients with COVID-19 on ventilators or receiving oxygen
therapy.
The advice
is not intended for critical care units but can be adapted for that use.
The dose
used in RECOVERY — 6 mg daily for 10 days — is five- to sixfold greater than
the therapeutic glucocorticoid replacement dose.
High glucocorticoid doses can exacerbate
hyperglycemia in people with established diabetes, unmask undiagnosed diabetes,
precipitate hyperglycemia or new-onset diabetes, and can also cause
hyperglycemic hyperosmolar state (HHS).
The guidance
recommend a target glucose of 108-180 mg/dL and up to 216 mg/dL is "acceptable."
Use of once-
or twice-daily NPH insulin is recommended for patients whose glucose has risen
above 216 in some cases with the addition of a long-acting analog.
The guidance
says that patients already taking premixed insulin formulations can continue
using them while increasing the dose by 20% to 40%.
Given the
risk of hypoglycemia associated with those formulations, many experts say they
would switch those patients to NPH during the time that they're on
dexamethasone.
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