The Centers for Disease Control and Prevention (CDC) holds that the number of those skipping their important second dose has increased from about 3.4 percent in March, more than double the rate among people who got inoculated in the first several weeks of the nationwide vaccination campaign.
The inoculation of the Pfizer and Moderna vaccines requires people to return for a second shot three or four weeks after the first dose to be fully effective. Anthony Fauci, the top U.S. infectious disease expert, was "not surprised" about this as it happens frequently with multi-dose vaccines.
"Obviously whenever you have a two-dose vaccine, you're going to see people who for one reason or other -- convenience, forgetting, several other things -- just don't show up for the second vaccine," said Fauci, as CNN reported.
Currently, 37 percent of the U.S. adult population is fully vaccinated and nearly 54 percent have received at least one dose. Experts have attributed the sluggish vaccine demand to factors including vaccine hesitancy. Nevertheless, they added that further analysis is needed.
The CDC maintains that people who are fully vaccinated can walk around in public spaces without masks except when there are large crowds.
"There are many situations where fully vaccinated people do not need to wear masks, particularly if they are outdoors," CDC Director Rochelle Walensky said.