How Well Does Pfizer Vaccine Protect Against Delta Variant?

Data from Israel’s health ministry shows Pfizer Covid-19 vaccine significantly less effective at preventing infection and symptomatic illness with the Delta variant than with previous strains of coronavirus; conflicting with existing research that suggests strong protection against the variant; here’s what might explain the discrepancy.

Key Facts about Pfizer:

• A full course of the Pfizer-BioNTech vaccine is 64% effective at preventing infection and 64% at preventing symptomatic Covid-19 caused by the Delta variant; according to preliminary findings from a study by Israel’s health ministry.
• The findings conflict with a number of other studies assessing the pfizer vaccine’s performance against the variant, which indicate a much higher degree of protection against infection and mild illness (between 80% and 90%).
• Since the researchers have not released the full data from the Israel study; it is difficult to fully assess the findings, Dr. Deepti Gurdasani; an epidemiologist at Queen Mary University in London told.

• But one potential explanation for the discrepancy is that the Israel data is just “the best we’ve got,” Dr. David Strain, a senior clinical lecturer at the University of Exeter told; pointing to Israel’s high proportion of fully vaccinated people; mature vaccination program and high prevalence of the Delta variant.
• The study did not take the steps needed to rule out these alternate explanations; such as Israel’s surveillance program potentially picking up more cases than other studies. It was due to most people in the highly vaccinated country only getting tested after contact with a positive case; Weintraub said, making it hard to conclude the vaccine is less effective.

Percentage of Illness Cured:

Lastly, 93%. That’s how effective the Pfizer vaccine is at preventing serious illness and hospitalization. Which is caused by the Delta variant after two doses, according to the Israeli study. This is only slightly lower than against other variants. “When you look at it; that means the vaccine is doing its job really well;” Strain said, given this is the key purpose of a vaccine. The “downside,” however, is that we may start seeing the virus spreading again.