Hong Kong, May 23 : Hong Kong residents will need to get vaccinated against Covid-19 if they want to travel abroad, Chief Executive Carrie Lam announced on on Sunday. "When the SAR (special administrative region) government discusses travel arrangements with other countries or places, it will require Hong Kong residents to be vaccinated, to make sure they would not be infected when they are abroad, and would not bring the virus back to Hong Kong," Lam wrote on social media, in a discussion about the government's plan to tackle the fact that relatively few residents have availed themselves of vaccines. The World Health Organization (WHO) say that at least 60 per cent of any population need to be vaccinated to achieve herd immunity. Hong Kong has struggled to get 20 per cent of its residents to get vaccinated with their first dose, dpa news agency reported. Critics blame Hong Kong's vaccine hesitancy on the lack of trust people have in the government, following two years of anti-government protests that were brought to an end with a national security law that went into effect almost a year ago, bring with it a vast changes to the city. Safety concerns have also stifled the roll-out of Covid-19 jabs, after the government briefly halted its vaccination programme in March amid packaging concerns about a batch of Pfizer/BioNTech vaccines, a move that further knocked public confidence. Meanwhile, experts say that vaccinations have a limited shelf life and warn that centres will close operations in September. /IANS