NEW YORK — The rate of vaccination against COVID-19 has been declining in the United States since early this spring, even as new, potentially deadlier variant strains of the disease emerge. In response, several major retail pharmacy operators are offering incentives to encourage people to take advantage of the availability of free vaccination.

The decrease in daily vaccinations began in April, when government health officials paused administration of the Johnson & Johnson vaccine for 11 days to investigate reports of rare side effects. According to a New York Times analysis of data from the Centers for Disease Control and Prevention (CDC), though, several states also experienced declines in first-dose applications using the Pfizer and Moderna vaccines in early April.

While some officials have stated that such a slowdown was expected around that time, there is concern that vaccine hesitancy among a large percentage of the unvaccinated population is proving to be an obstacle to the federal government’s goal of having 70% of the adult population inoculated by July 4. According to a recent CDC household pulse survey, 17.6% of all adults polled are hesitant about receiving a vaccine.

The Biden administration, which aggressively recruited pharmacies to provide mass inoculation as vaccines became available at the start of the year, has called on them again to help revive the rate of vaccination through incentive programs and offers.

For example, Kroger Co.’s Kroger Health division has launched a #CommunityImmunity giveaway campaign that gives customers and employees the opportunity to win prizes ranging from free groceries for a year to one of five $1 million payouts.

“It’s exciting that Kroger is using innovative tactics to encourage vaccinations among its millions of customers across the country,” said Ian Sams, deputy assistant secretary for public affairs at the Department of Health and Human Services. “Businesses like Kroger are stepping up to the plate to encourage vaccinations as we pursue President Biden’s goal of having 70% of adults with at least their first dose by Independence Day.”

For its part, CVS Health is holding a sweepstakes offering more than 1,000 prizes for eligible customers who received or plan to receive a vaccination through CVS. CVS is offering 125 giveaways of $500 and five Grand Prize giveaways of $5,000 for family reunions. Other prizes offered in partnership with suppliers include a VIP trip for two to Super Bowl LVI in Los Angeles, including airfare, hotel and more (with Procter & Gamble Co.), and 100 seven-day cruises for two to a destination of choice (with Norwegian Cruise Line).

Meanwhile, Hy-Vee Inc. is giving $10 gift cards to anyone who completes their vaccination at a Hy-Vee pharmacy or pop-up vaccination clinic between June 1 and November 11.