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until today
we've only really had an outline of the
science behind
any of the covid vaccines but now it's
become a bit clearer
instead of press releases and little
bits of detail gleaned from the uk
regulator
we now have what scientists would regard
as more of the meaty detail
today we saw the publication of efficacy
and safety analyses from the oxford
astrazeneca vaccine trials we've also
seen a much
fuller data set of the pfizer bayern
tech vaccine trial
that's because before the u.s regulator
the fda
discusses the possible approval of a
drug or a vaccine
it publishes a synopsis of the submitted
evidence
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so what have we learned about how well
they protect people from getting ill
from covid
we got more detail on the headline
results of the oxford trial
you may remember it returned two results
the largest study group who were given
two full doses
showed 62 efficacy we now know the range
of uncertainty
that figure could be as low as 41 or as
high as 75.7
these figures are what is known as
confidence intervals
meanwhile a much smaller group who were
given a low dose followed by a higher
dose
in a move that was not initially planned
showed 90
efficacy with confidence intervals of
67.4 and 97
we need to be careful interpreting this
there may not be
a big difference between the doses
pfizer's large trial showed 94.6
efficacy with smaller confidence
intervals of 89.9
and 97.3
one issue that has been flagged with
oxford's vaccine is that there were very
few older people involved in the
analysis
for the low-dose standard dose group
everyone was under 55
so we don't know how well it works in
older people
there was quite consistent efficacy
between different age groups and races
but we've got to remember we're talking
about around 190 symptomatic infections
and they're spread across these
different age groups and race groups so
it's difficult to be sure about the
reliability of each comparison but i
think we need to look at the overall
results and see that this was
a very powerful vaccine in terms of
stopping people getting sick
with coco this isn't just about
illness it's about controlling the
spread of the virus
one of the big questions is whether the
vaccine is able to prevent
people who get the virus but don't
display symptoms from spreading the
virus
unlike the other trials oxford took
weekly swabs to identify infections
so we're able to pick up asymptomatic
cases
other trials only looked at people with
symptoms and didn't test more widely
for the virus there is some evidence
that oxford's low-dose
standard dose combination might prevent
asymptomatic infection
there was a 59 reduction but it's very
uncertain
because those numbers involved are so
small the confidence interval range
is huge it's from one percent to 83
percent
when the combination of two standard
doses was used
there was essentially no reduction in
asymptomatic infection
the figure was four percent with very
wide confidence intervals
of minus 72 percent to 46
this might mean more data and analysis
are needed
we weren't expecting this disconnect
between a vaccine's effect on symptoms
and a vaccine's effect on overall
protection and if we see the same shift
for the fires from modern vaccines it's
an important thing to know because
it affects how you deploy the vaccine
you might need much higher
coverage levels to actually achieve
eradication in the long term
both trials report that there were more
mild adverse effects in the vaccine
groups than in the control group
these included fatigue fever and
headache
most vaccines produce any harm that they
have
within two months occasionally there
will be problems at four months
and it's pretty rare to find problems
that go beyond that but we still need to
be sure
so the really key next steps will be
surveillance
of those who've been vaccinated
margaret keenan made history today as
the first person vaccinated for covid
outside of a trial
we have a vaccine but what exactly that
means yet for us all
is less clear