How many more reinforcements will be needed?

As people give themselves booster doses, many wonder how many more will be needed for adequate protection against COVID-19.

Maybe not so many.

Repeating booster doses every four months could eventually weaken the immune response and tire people out, the European Medicines Agency (EMA) warned last week.

Instead, countries should allow more time between booster programs and leave them for the start of the cold season in each hemisphere, following the flu vaccination strategy plan, the regulator said.

That contrasts with comments from the UK, where the government’s advisory panel on inoculations said there is no immediate need for a second booster for the most vulnerable.

Some three months after the third vaccination, protection against hospitalization among those over 65 remains at around 90%, according to data from the UK Health Security Agency. With just two doses, protection against serious illness drops to around 70% after three months and 50% after six months. The figures will be revised as they evolve.

The boosters”they can be done once, or maybe twice, but it is not something that we think should be repeated constantly”, said Marco Cavaleri, director of strategy for vaccines and biological threats to health, at a press conference. “We need to think about how we can transition from the current pandemic environment to a more endemic environment.”

Meanwhile, Pfizer is developing a hybrid vaccine that combines its original vaccine with a formulation that protects against the highly transmissible omicron variant.

Pfizer will test the new hybrid formulation against an omicron-specific vaccine and determine which is more suitable to move forward with in March, Chief Executive Officer Albert Bourla said at a JPMorgan conference last week.

Pfizer will be ready in March to approach US regulators to get the modified vaccine approved and bring it to market. Bourla added that production has already started.

In Europe, regulators said April is the earliest they could approve a new vaccine targeting a specific variant, as the process takes three to four months.