'It's booster time' - EU agencies back third shot for all in U-turn

But it is seen a major U-turn from its previous guidance - which in September suggested that booster shots should only be given to the elderly and those with weakened immune systems, arguing that there was no need to administer those to the general population.

"Filling the immunisation gap is a priority," since this gives ample room for the virus to spread, the director of the ECDC Andrea Ammon said.

But boosters shots can help to reduce the transmission of the virus, she added.

It is estimated that, with the arrival of the Delta variant, the efficacy of the vaccine against transmission has fallen from 60 to 40 percent, while data suggest that the effect of the second dose gradually begins to wear off after some months.

Across the EU, nearly 66 percent of the entire population is fully-vaccinated - but there are significant differences between member states.

Croatia, Slovakia, Romania and Bulgaria are still reporting less than 50 percent of full vaccine uptake, while only a few countries have reached the 75-percent threshold recommended by health authorities.

"But there are still sub-populations and age groups in which coverage remains lower than desired, even in countries that have achieved good overall vaccination coverage," Ammon warned.

Echoing the same argument, Marco Cavaleri, in charge of vaccines strategy at the European Medicines Agency (EMA), said the boosters can make vaccines three times more efficient and help reduce transmission for a longer period.

"It is booster time" for all those who received their full vaccination six months ago, he said.

However, the EMA has only approved the use of Pfizer or Moderna booster shots, while it is currently assessing the third dose of the Johnson & Johnson vaccine.

To date, Pfizer, Moderna, Johnson & Johnson and AstraZeneca are the only jabs approved in the EU.

Meanwhile, the EMA is also assessing various new medicines that can help reduce hospitalisation and deaths of patients at risk of severe Covid-19, as well as the so-called vaccine cocktails, based on the idea of blending different shots.

In the EU, the Czech Republic, Slovakia, Romania, Bulgaria, Hungary, Germany and Greece are offering a third dose to citizens of all ages. And Belgium recently said that it will do so from early 2022.

'No magic wand'

Austria recently announced it would imposed mandatory vaccination from February next year, becoming the first country in the EU to take such approach, and inspiring similar debates in neighbouring countries.

The German health ministry is mulling making vaccination compulsory for workers in nursing homes and clinics from 2022, according to Spiegel magazine.

Mandatory vaccination should be considered "if we are not able to convince more people with good arguments and medically-justified advantages for vaccinated people," German MEP Pieter Liese told EUobserver.

However, Ammon called for caution on this approach, arguing that "mandatory vaccination is not a magic wand" and could have the opposite effect, since "it could drive people into rejecting more the vaccines".

Christmas at risk

During the Christmas season, activities such as social gatherings, shopping or travelling, pose "significant additional risks for intensified transmission of Delta," the ECDC warned, recommending countries to reimpose restrictive measures.

These include increasing the use of face masks, imposing teleworking, reducing crowding on public transports, limiting for the number of attendees in public events, and putting in place prevention measures in schools and other educational centres.

Additionally, the ECDC has called on member states to continue sequencing positive samples in order to detect the emergence of new variants.