Although immunizations are effective against the Delta Variant, the extent of protection provided appears to depend on whether or not you have completed your vaccination course. According to a study published in the journal Nature on Thursday, a single dosage of Pfizer’s or AstraZeneca’s vaccinations – both of which require two shots – was either wholly or weakly ineffective against Delta.
Blood samples from persons who had gotten one of those shots were used in laboratory experiments by the researchers. Only 10% of those samples generated antibodies that neutralized the Delta Variant after a single injection, indicating that they would be protected from symptomatic infection.The researchers concluded that the Delta variation “partially but significantly evades” immune vaccination protection. While the results of laboratory tests like this don’t often apply to the real world, other studies have found that Delta is resistant to vaccine protection after just one shot.
In May, a UK study indicated that a single dose of Pfizer’s or AstraZeneca’s COVID-19 vaccination was only 33% effective against symptomatic COVID-19 induced by Delta. After two doses, Pfizer’s vaccine had an efficacy of 88 percent, whereas AstraZeneca’s had a 60 percent efficacy. Two doses of Pfizer’s vaccine were also 96% effective in reducing Delta-related hospitalizations, while two doses of AstraZeneca’s vaccine were roughly 92% effective by the same measure.
Meanwhile, Canadian research that has yet to be peer-reviewed indicated that a single dosage of Pfizer’s injection was 56 percent effective at avoiding symptomatic Delta Variant infections after two weeks. AstraZeneca’s injection had a 67 percent success rate, whereas Moderna’s had a 72 percent success rate. When it came to avoiding Delta-related hospitalizations, Pfizer had a 78 percent efficacy, AstraZeneca had an 88 percent efficacy, and Moderna had a 96 percent efficacy.