The Food and Drug Administration has postponed Pfizer’s request for emergency use authorization of its COVID vaccine for children aged 6 months through 4 years old. Pfizer says a clinical trial showed two low doses of its vaccine had limited efficacy at preventing disease among 2-to-4-year-olds. Pfizer is now evaluating whether a third dose produces a stronger immune response in young children.

In other medical news, a new study finds COVID-19 can substantially increase the risk of cardiovascular disease, even in fully recovered patients with mild cases. The research, published in Nature Medicine, found the risk of stroke was increased by over 50% and the risk for heart failure increased by over 70% in the year following an infection for unvaccinated people.

The World Health Organization’s director-general called for a waiver on intellectual property protections for COVID vaccines during a tour of a South African vaccine producer. Tedros Adhanom Ghebreyesus said ending the “acute phase” of the pandemic is within reach if 70% of the world’s population is inoculated by mid-year.

Tedros Adhanom Ghebreyesus: “It’s not a matter of chance; it’s a matter of choice. So if the world wants to end it, it has the means to end it. If it wants to continue to be greedy and doesn’t want to end it, then it will not end.”