After the second dose, vaccine efficacy from two standard doses is 82.4% with the three-month interval being used in the United Kingdom, researchers from the University of Oxford say.
A total of 118,767 persons have been vaccinated in the five days since vaccine administration began in the island.
However, the first dose did not provide protection against asymptomatic infection in the same period.
The AstraZeneca vaccine against COVID-19, one of the vaccines Morocco is using in its national vaccination campaign, could "substantially" reduce the spread of the virus, a preliminary study has found.
They report that the effect of dosing interval on efficacy is pronounced, with vaccine efficacy rising from 54.9% with an interval of less than six weeks to 82.4% when spaced 12 or more weeks apart.
It was more effective to wait 90 days than to administer the second dose, researchers found, "providing further support for current policy".
This study - on 17,000 people in the UK, South Africa and Brazil - showed protection remained at 76% during the three months after the first dose.
The Sputnik V vaccine was rolled out in some countries before the final trial data had been released, provoking concerns among some scientists. Some of the participants who initially consented to a single dose study did not choose to receive the second dose, providing a self-selected cohort of single-dose recipients. Last week, Germany's vaccine committee recommended it should only be given to people aged under 65, while the European Union, which authorized it on Friday for people aged 18 and over, lowered its reported efficacy rate from 70.4% to 60%. "In addition, data from an additional month of follow-up is now available for inclusion in the analysis, providing greater precision in estimates due to the larger number of cases for analysis in comparison with the previous report", they write. They noted this included the subset of British participants who received a half-dose vaccine as their first dose when interim analysis data was reported in December. The jab has come under scrutiny because of the dosing error in the Oxford trial and a paucity of data about its efficacy in older people who are most vulnerable to the virus.