Outbreaks in economies that vaccinated early such as Israel and new studies have raised doubts about the durability of vaccine protection and prompted booster rollouts. How much has the efficacy of major Western vaccines waned over time and how much will boosters help?
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We first show that lower recent estimates of vaccine efficacy against infections reflect a reduction in the immune response to vaccines over time, higher vaccine resistance of the Delta variant, but also biases in several real world studies.
Averaging across the most robust studies, we document that vaccine efficacy against infections tends to diminish significantly over time from around 80% a month after full vaccination to around 55% five months after vaccination. In contrast, vaccine efficacy against symptomatic infections and especially hospitalizations diminishes less over time, with an estimated efficacy against hospitalizations of around 90% six months after vaccination.
Finally, we document early evidence from Israel which suggests that booster shots return vaccine protection against infections to high levels and should raise protection against hospitalizations even higher.
David Llewellyn-Smith is Chief Strategist at the MB Fund and MB Super. David is the founding publisher and editor of MacroBusiness and was the founding publisher and global economy editor of The Diplomat, the Asia Pacific’s leading geo-politics and economics portal.
He is also a former gold trader and economic commentator at The Sydney Morning Herald, The Age, the ABC and Business Spectator. He is the co-author of The Great Crash of 2008 with Ross Garnaut and was the editor of the second Garnaut Climate Change Review.
