A single dose of Pfizer’s coronavirus vaccine may not generate a sufficient immune response to protect against dominant new variants, except in people who have already been infected with Covid-19, according to a UK study published on April 30.

BioNTech expects results by September from trials testing the Covid-19 vaccine developed with Pfizer in babies as young as 6 months old, German magazine Spiegel cited the company’s CEO as saying.

The U.S. Centers for Disease Control and Prevention (CDC) has not found a link between heart inflammation and Covid-19 vaccines, the agency’s Director Rochelle Walensky said on April 27.

The Covid-19 vaccine developed by Pfizer and BioNTech is effective at preventing symptomatic and severe disease in people with some chronic illnesses, like diabetes and heart disease, the biggest real-world study showed on April 22.

The U.S. Centers for Disease Control and Prevention (CDC) said up to 5,800 people who have been fully vaccinated against coronavirus disease 2019 have been infected by the novel coronavirus following vaccination.

The first study to directly compare immune reactions between Pfizer’s and AstraZeneca’s Covid-19 vaccines found strong and broadly similar antibody responses in over-80-year-olds after a first dose of either shot, scientists said on April 14.

Pfizer Inc. and the company’s German partner BioNTech SE on April 9 asked U.S. regulators to allow the emergency use of their vaccine in adolescents aged 12 to 15 years old.

A follow-up study of 33 people who received Moderna Inc.’s Covid-19 vaccine in early trials show the antibodies it induced are still present six months after the second dose.

The U.S. National Institutes of Health said on April 7 it had begun a mid-stage study to determine the risk of allergic reactions to Covid-19 vaccines made by Moderna Inc. and Pfizer Inc.

An open question is how long the current Covid-19 vaccines will offer protection against the virus. Will they provide lifelong protection like some vaccines, such as polio, or seasonal, like influenza?