Geneva (AFP)

As the good news on a Covid-19 vaccine brings a wave of optimism, public mistrust of immunization could render the most effective of products useless, warns the head of the WHO's immunization division.

"A vaccine that remains in a freezer or refrigerator or on a shelf and is not used does nothing to stop this pandemic," Katherine O'Brien told AFP in an interview by videoconference on Friday.

On Monday, the American Pfizer and the German BioNTech announced that their vaccine was 90% effective, according to preliminary results of their vaccine tested in phase III on more than 40,000 people.

Professor O'Brien judged these results, even preliminary, to be "extremely important" and she said she hoped that data from several other vaccines, also in the last phase of human testing, would follow soon.

But, she is deeply concerned about the disinformation and conspiracy theories that are growing the ranks of anti-vaccine, when the pandemic is far from being under control and has already claimed nearly 1.3 million lives.

There is a need to increase "confidence that the WHO will not make any concessions on the safety or efficacy of the vaccines it is evaluating".

- Gigantic logistical challenge -

Dr O'Brien acknowledged that there remained a number of important unknowns regarding vaccine candidates, such as the length of protection they will be able to offer and perhaps equally important the big question: "Does this change- is there the likelihood that you can transmit (the disease) to someone else? "

The WHO is counting on the arrival of these vaccines in the coming months but is preparing without delay for the gigantic logistical challenge of inoculating billions of people as quickly as possible.

In the meantime the WHO has developed recommendations to give the first vaccines to those who need them most.

"The goal is for each country to be able to immunize 20% of its population by the end of 2021, which would really help meet the needs of health workers and the highest priority populations, then, as the supply will continue to increase, we expect to receive many more doses in 2022 ", explains Katherine O'Brien.

Access will also depend on the ability to manufacture the vaccines in astronomical quantities, to package them, to transport them sometimes while keeping them frozen at very low temperatures and then to find sufficient personnel to inject them.

"A highly effective, safe, and manufacturable vaccine is only of public health value if it actually reaches the people it needs to protect and if it is widely used by populations. That is the next challenge. that awaits us, ”she said.

“I recently heard an analogy that demonstrating the efficacy and safety (of a vaccine) is like setting up a base camp at the foot of Everest.

"But in reality, to achieve a real impact of vaccines, it is at the level of its distribution that it is played out and that means climbing Everest", underlined Katherine O'Brien.

© 2020 AFP