WASHINGTON (REUTERS) - United States health officials, after meeting with vaccine maker Pfizer, reiterated on Monday (July 12) that Americans who have been fully vaccinated do not need to get a booster shot, a spokesman for the Department of Health and Human Services (HHS) said.

Pfizer said last week it planned to ask US regulators to authorise a booster dose of its Covid-19 vaccine, based on evidence of greater risk of infection six months after inoculation and the spread of the highly contagious Delta variant.

HHS officials had a briefing from Pfizer on Monday regarding its latest, preliminary data on vaccinations and will continue to discuss when and if booster shots will be needed in the future, the spokesman said.

Pfizer said it planned to publish "more definitive data" in a peer-reviewed journal.

"Both Pfizer and the US government share a sense of urgency in staying ahead of the virus that causes Covid-19, and we also agree that the scientific data will dictate the next steps in the rigorous regulatory process that we always follow," said Pfizer spokesman Sharon Castillo.

The spread of the Delta variant, first detected in India and now the dominant form of new coronavirus infections in many countries, has raised concerns over whether available vaccines offer enough protection.

Several experts say a booster shot would be warranted if there is a substantial increase in hospitalisations or deaths among vaccinated people.

For its part, the World Health Organisation said on Monday that rich countries should not order booster shots for their vaccinated populations while other countries have yet to receive Covid-19 vaccines.