New Delhi, April 3 : In the wake of rising Covid cases, several countries including the UK and New Zealand have rolled out another booster dose, while Canada and the US are planning to introduce the shots. Last week, the World Health Organisation (WHO) updated its Covid-19 vaccination recommendations, saying healthy children and adolescents may not necessarily need a vaccine, while the elderly and at-risk groups should receive an additional booster dose six to 12 months after their last dose. The revised recommendations reflect the impact of Omicron and high population-level immunity due to infection and vaccination. The UK has begun booster shots since April 1 for people who are 75 and older, or who live in a care home for older adults, or who are 5 years and older and are immunocompromised should be offered a spring booster, as long as it has been six months since their last shot. This comes after last year, 82.5 per cent of people aged 75 and older received a bivalent booster in the country. "To protect the most vulnerable in the population against becoming seriously unwell with Covid-19, JCVI's view is that the provision of a spring booster dose for these people is a proportionate response in 2023," the UK Health Security Agency (UKHSA) said in a statement. "Covid-19 is still circulating widely, and we have recently seen increases in older people being hospitalised," said Mary Ramsey, the head of immunisation for the UKHSA. Beginning April 1, New Zealand also started Covid booster shots -- a bivalent booster for all citizens over 30 -- ahead of the peak flu season. The bivalent vaccine contains two strains or components of the virus, widening the net of immunisation, and has replaced the Pfizer booster vaccine. "People at higher risk of severe illness from Covid-19 will also be able to receive an additional booster, regardless of how many doses they've previously had," Minister of Health Ayesha Verrall was quoted as saying by the local media. In March, Canada's National Advisory Committee on Immunization (NACI) recommended a spring shot for high-risk individuals - those with severe illness, including immunocompromised adults and elderly. In its new recommendation NACI, outlined that an additional vaccine dose may be offered at a standard interval, six or more months from the last Covid-19 vaccine dose or SARS-CoV-2 infection, whichever is longer. NACI wrote that bivalent, Omicron-containing, mRNA-based Covid-19 vaccines are the "preferred" option for booster shots. The US Food and Drug Administration (FDA) is also considering the current Covid situation and is likely to authorise a second booster with the bivalent vaccines for at least some people, such as those who are at high risk because they have compromised immune systems or are 65 and older, a federal official who was not authorised to speak publicly was quoted as saying to NPR. A decision could be announced within weeks, the report said. /IANS