WASHINGTON: Vaccination of about 88 per cent of Americans who received the first dose of Pfizer-BioNTech or Moderna's COVID-19 vaccines was complete, a study of over 12 million people by the US Centers for Disease Control and Prevention (CDC) showed.
Both vaccines, among the firsts to receive US emergency use authorisation, require two shots. The vaccines' high efficacy is based on trials with interval between the shots of 21 days for Pfizer-BioNTech and 28 days for and Moderna's vaccine.
According to the analysis, about 3 per cent of people in the United States who received the first dose of either of the vaccines did not get the second dose needed to complete vaccination, the agency said on Monday.
The agency said 8.6 per cent had not received the second dose, but were still within the allowable interval to receive it.
The analysis was conducted in 58 jurisdictions in the United States among people who got their first shot between Dec 14 and Feb 14. The data was published in the Morbidity and Mortality Weekly Report on Monday.
A second analysis of 14.2 million people who have received the second dose showed that 95.6 per cent received the dose on time, the agency said.
The CDC considered a second shot on time, or within the recommended interval, if it was given within 17-25 days after the first dose for Pfizer-BioNTech, and 24-32 days for Moderna vaccine.
Other countries, such as the United Kingdom, have stretched the time period between doses to months rather than weeks in order to vaccinate more people as they deal with supply shortfalls. US public health officials have said they do not intend to make any changes in their recommendations.