Vaccine effectiveness

BioNTech (NASDAQ:BNTX) and Pfizer (NYSE:PFE) shares weakened in Tuesday's premarket as a study in Israel found that in recent weeks their vaccine began to lose effectiveness in preventing the COVID-19 delta strain and the occurrence of symptomatic infections. However, according to the Israeli government, the vaccine continues to provide reliable protection against severe forms of COVID-19 infection.

BioNTech shares fell more than 5% and Pfizer shares fell 0.6%.

The RNA messenger-based vaccine developed by the two companies has been one of the most effective treatments for COVID-19 on the market so far.

Its success in protecting people from infection dropped to 64% between 6 June and early July from the previous 94%, according to the study. The drop in effectiveness came against the backdrop of the spread of the delta strain in Israel, the Ministry of Health said. This also coincided with the lifting of quarantine restrictions in early June.

Despite signs of an increase in infections, the data still show that the vaccine protects people from serious illness. Its effectiveness in preventing hospital admissions has fallen to only 93%, compared with at least 97% according to an earlier government study, suggesting that it is still very effective in such cases.

The more aggressive delta strain, which first appeared in India, is spreading worldwide. The mutation of the virus has forced some countries to postpone or revise plans to ease restrictions on business, activities and travel.