Though countries in the West have recommended boosters for all adult population, the evidence to use them is highly tilted towards the elderly population, those who are immunocompromised and frontline workers. WHO has also recommended boosters for those jabbed with the inactivated virus vaccines (by companies such as Sinovac, Bharat Biotech). For the immune-compromised and the elderly, the booster is a way to keep generating antibody response. Boosters for healthcare workers ensure their protection and thus lower the burden on the healthcare system.
What other countries are doing?
India has recommended boosters (precautionary dose) nine months after the second vaccination. The US CDC has recommended boosters after two doses of the mRNA vaccines (Pfizer/Moderna) and two months after first dose of adenovirus vaccine (J&J). The UK recommends boosters after three months and Singapore after five months.