LONDON (AP) — An expert advisory panel recommended Tuesday that the U.K. government offer a third dose of COVID-19 vaccine to everyone over age 50 to protect against waning protection this winter.

The Joint Committee on Vaccination and Immunization’s recommendation came as Prime Minister Boris Johnson prepared to announce the government’s new plan for combating the pandemic. The World Health Organization has asked wealthy nations to delay booster shots until every country has vaccinated at least 40% of their populations.

The JCVI said booster shots were needed to ensure vulnerable people are protected against COVID-19, because studies have shown that the immunity conferred by vaccines weakens over time. The panel recommended that people over 50 get a booster shot six months after they received their second dose of vaccine.

The move comes despite appeals from WHO, which has urged rich countries with large supplies of coronavirus vaccines to refrain from offering booster shots through the end of the year and make the doses available for poorer countries.

WHO Director-General Tedros Adhanom Ghebreyesus appealed last week for restraint, saying he couldn’t stay silent when companies and countries that control the global supply of vaccines think the world’s poor should be satisfied with leftovers.

Israel has been providing third doses to a wide range of people who already received a full two-dose regimen months earlier. U.S. health officials are continuing to assess the science and utility of boosters.

WHO officials insist the scientific justification for boosters remains unclear.

Oxford University Professor Sarah Gilbert told The Telegraph newspaper last week that immunity from the vaccine was holding up well — even against the delta variant. While the elderly and those who are immune-compromised may need boosters, the standard two-dose regimen is providing lasting protection for most people, she said.

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