Tokyo, Oct 29 : The Japanese Health Ministry has planned to begin offering Covid-19 booster shots in December, starting with medical workers, local media reported. The Ministry held an expert panel meeting on Thursday to discuss the details of delivering the booster shots and planned to make an official decision in November, reports Xinhua news agency. The results of a US study showed that the efficacy of the Pfizer vaccine changed differently among different age groups five months after taking the second shot. The efficacy declined from 89 percent to 39 percent in the 16 to 44 age group, from 87 per cent to 50 per cent in the 45 to 64 group, and from 80 per cent to 43 per cent in people aged 65 or older. The panel urged the Ministry to promote booster shots for elderly people and others with a high risk of turning severe cases, as the vaccine efficacy for them is expected to decline over time. The US offers a third shot for elderly people and those aged 18 or older with potential health issues, and Israel provides a booster vaccine for everyone aged 12 or older who received two shots. /IANS