Spain's health ministry said Thursday it would give third doses of coronavirus vaccines to the over-70s, hoping to improve their protection against Covid-19.

The National Public Health Commission has decided to offer the booster jab vaccinations from late October to elderly people who received a second vaccine dose more than six months ago, the ministry said in a statement.

Spain had until now only offered third doses to care home residents and some people with compromised immune systems.

"The aim is to increase protection of the most vulnerable," the ministry said.

Europe's medicines watchdog on Monday approved a third dose of the Pfizer-BioNTech vaccine for over-18s, against a background of fears their protection against the virus could diminish over time.

The European Medicines Agency (EMA) has also approved booster doses of both the Pfizer and Moderna shots for seriously immunocompromised people.

More than 15 countries worldwide have begun issuing third doses, including in European Union nations including France, Italy and Germany.

Eyeing a potential winter resurgence of Covid, some countries did not wait for EU authorities' approval for their schemes.