Pfizer, Moderna COVID-19 Boosters Effectiveness Wanes After Four Months: CDC Study

COVID-19 vaccine boosters from Pfizer Inc PFE / BioNTech SE BNTX and Moderna Inc MRNA become less effective after four months but still provide significant protection against hospitalization, a CDC study found.

• While vaccine efficacy was still strong two months after a booster shot, it declined significantly after four months.
• Efficacy against COVID-19–associated emergency department visits and hospitalization was 87% and 91%, respectively, during the two months after a third dose and decreased to 66% and 78% by the fourth month after a third dose. 
• Related: Menstrual Irregularities Cases After mRNA COVID-19 Vaccine - EMA Reviews Cases.
• Protection against hospitalizations exceeded that against emergency department visits.
• Researchers said the results suggest that additional boosters may be needed.
• "The finding that protection conferred by mRNA vaccines waned in the months after receipt of a third vaccine dose reinforces the importance of further consideration of additional doses to sustain or improve protection against COVID-19–associated ED/UC encounters and COVID-19 hospitalizations," CDC wrote.
• Price Action: MRNA shares are down 12.1% at $141.84, PFE stock is down 2.86% at $49.33, and BNTX shares are down 8.59% at $156.27 during the market session on the last check Monday.