PARIS, Jan 6, 2022 (BSS/AFP) - Two years ago, a previously unknown virus
plunged humanity into an unprecedented global crisis that has transformed our
daily lives -- and significantly expanded scientific knowledge.

  - In the air -

  In the early months of the pandemic, the prevailing scientific advice was
that frequent handwashing would help stop the spread of Covid-19.

  Health authorities urged people not to touch their faces with soiled hands
and shared techniques on how to apply soap, while in many countries hand
sanitisers became ubiquitous.

  But as the pandemic wore on and scientists were able to study real world
examples of how the virus spread -- at a choir practice, in a bus or across a
restaurant -- a consensus emerged that this disease was largely transmitted
through the air.

  The virus travels in clouds of particles that we emit when we breathe and
especially when we speak, shout or sing.

  In a closed and poorly ventilated room, these aerosols can float and drift
in the air for a long time, greatly increasing the risk of infection.

  But the importance of good ventilation to disperse these contaminated
clouds -- like clearing cigarette smoke -- is not always well understood by
the general public.

  "There was a communication error: we scientists were not clear enough about
ventilation," said Arnaud Fontanet, of France's Scientific Council, a body
that guides government policy.

  "When scientists talk about protective measures, we have to make it clear
to people that ventilation is a part of it," he told AFP.

  - Flip-flop on face coverings -

  As a direct result of the awareness of aerosol transmission, the discourse
on masks has radically changed in two years.

  Initially, the World Health Organization (WHO) and many governments
insisted that masks should only be used by caregivers, patients and their
close relatives and not by the general public.

  But many supporters of generalised mask wearing saw that as a way to
conserve limited supplies and prevent a shortage for caregivers.

  By spring 2020, there was an abrupt policy change and the mask became an
essential tool in the fight against the pandemic, becoming mandatory in some
places.

  As more contagious variants have emerged, people have been advised to ditch
their simpler fabric masks in favour of the super filtration of surgical
masks.

  And with the surge of the extremely contagious Omicron variant, many
scientists are now advising people to wear even more protective masks like
the FFP2 or N95 when in crowded indoor spaces.

  - Vaccines: a game changer -

  The coronavirus has claimed millions of lives around the world since it
first emerged two years ago, but that toll would have been far higher if it
had not been for vaccines developed in record time.

  Against all expectations, the pandemic showed that it is possible to design
new vaccines against an unprecedented disease, and then start administering
them worldwide in less than a year. In the past, that process typically took
10 times longer.

  Just over a year after the start of the global vaccination campaign, around
half of the planet's population is fully vaccinated against Covid-19,
according to the University of Oxford's website Our World in Data.

  However, the vaccine rollout has confirmed fears that protection against
the virus would be mired in inequalities between rich and poor countries.

  WHO chief Tedros Adhanom Ghebreyesus wants 70 percent of the world's
population to be vaccinated by July and has called for an end to vaccine
hoarding by richer nations.

  "If we end inequity, we end the pandemic," he said in his New Year message.

  - ...but no magic bullet -

  Vaccines have been hugely effective at protecting against serious forms of
Covid-19.

  But they have been less effective at stopping the pandemic because they do
not prevent people from spreading the virus.

  Their overall effectiveness also decreases over time, while they have been
shown to generate a weaker antibody response against the latest variants --
Omicron and previously Delta -- than against the historical strain of the
coronavirus SARS-CoV-2. Although there is mounting evidence that Omicron is
milder than previous variants, rich countries have scrambled to accelerate
booster campaigns to restore protection against infection.

  This has heightened fears that rich countries will continue to monopolise
vaccine doses, even as the virus spreads in poorer nations where people have
less access to protection.

  It is also not yet clear how long the effects of booster shots will last,
and experts have warned that relying on them can only be a short-term
strategy.

  The WHO's top Covid pandemic expert Maria Van Kerkhove stressed that
vaccines must reach vulnerable people around the world, while public health
measures like testing, isolation and masks will remain crucial.

  "Vaccines AND, not Vaccines ONLY will end the #COVID19 pandemic. No one
solution is enough," she tweeted.