NACI website on Wednesday, the committee said “current evidence suggests high vaccine effectiveness against symptomatic disease and hospitalization for several weeks after the first dose, including among older populations.” Here’s what the provinces, territories have said about AstraZeneca’s vaccine and seniors NACI said due to limited supply of COVID-19 vaccines, “jurisdictions should maximize the number of individuals benefiting from the first dose of vaccine by extending the interval for the second dose of vaccine to four months.”“Extending the dose interval to four months allows NACI to create opportunities for protection of the entire adult population within a short timeframe,” the committee said. “This will not only achieve.