Each new infection gives the virus a chance to mutate as it makes copies of itself, threatening to undo the progress made so far to control the pandemic.
Dr. Samantha Hill, a cardiac surgeon in Toronto, says because pregnant and breastfeeding women haven't been included in clinical trials yet she is worried the message many pregnant women are getting is to not get vaccinated.
More than 5 million people in the United States and millions more around the world have Alzheimer’s, the most common form of dementia.
Before any vaccine is permitted in the U.S., it must be reviewed by the Food and Drug Administration, which requires study in thousands of people.
Pfizer and its German partner BioNTech just last week estimated the vaccine was more than 90 per cent effective after 94 infections had been counted in a study that included 44,000 people.