Individuals who have not been vaccinated will need to be tested every three days to maintain their green status. A fully vaccinated person would do so every 30 days.
Sri Lanka has also been aggressively rolling out China's Sinopharm jab after receiving two million doses in the past week, opening its program to pregnant women on Wednesday.
Oxford/AstraZeneca is the most widely given vaccine, administered in 170 of the 215 countries where campaigns have begun.
It is followed by Pfizer/BioNTech, which is being used in at least 97 countries; Moderna (at least 46); Sinopharm (45); Sputnik V (40); Johnson & Johnson (29).
This afternoon, WHO gave emergency use listing to Sinopharm Beijing's Covid-19 vaccine, making it the sixth vaccine to receive WHO validation for safety, efficacy and quality.
Simao said the WHO's independent panel was assessing the Moderna vaccine and a vaccine from China's Sinopharm on Friday and was due to look at China's other main vaccine, made by Sinovac Biotech, next week.
"So, by the beginning of next week or the end of next week we will have the final assessment of these three vaccines out," she told a briefing.
Gao says one option is to adjust the dosage, the interval between doses, or increase the number of doses while the second route is to mix vaccines that use different technologies
More attention should be given to developing mRNA vaccines as the technology provided an opportunity for breakthroughs in treating all kinds of illnesses: health expert