NYC, California turn to COVID testing mandate to boost vaccination numbers -- will it be enough?

As contentious debates over vaccine mandates continue with new coronavirus cases on the rise among the unvaccinated, elected officials are starting to fine-tune the idea of a new incentive by requiring public employees to get a coronavirus test until they get their shots.

Barun Mathema, an assistant professor of epidemiology at Columbia University's Mailman School of Public Health, told ABC News that the plan is a very effective incentive on paper, and it will have a bigger impact outside of the public sector when it comes to confidence in the vaccines.

"This is saying the government, unambiguously, supports vaccination. One can try things like lotteries to entice individuals, but to me, this is a serious and thoughtful approach," he told ABC News.

New York City Mayor Bill de Blasio announced last week that employees of the city's public hospital system, which included medical centers like Elmhurst Hospital, the epicenter of the first wave of hospitalizations in 2020, would have to show proof of vaccination or submit a weekly test until they got their shot. Exemptions are allowed for religious medical reasons.

De Blasio expanded that order on Monday to all city public employees, which included police officers, firefighters and teachers. Even though 59% of the city's entire population and 70% of its adult population has at least one dose of the vaccine as of Tuesday, the numbers were lagging among the ranks of some New York agencies, city data showed.

The NYPD had a 43% vaccination rate, the Department of Correction had a 42% vaccination rate, the FDNY had a 55% vaccination rate, and public school employees and city hospital employees each had a 60% vaccination rate, according to data from city officials. Nationally, 56% of all residents and 69% of all adults have at least one shot, according to the U.S. Centers for Disease Control and Prevention.

The testing mandate will go into effect for unvaccinated public hospital workers next week, and goes into effect on Sept. 13, the first day of schools in New York, for other public employees.

De Blasio stressed that the delta variant is causing cases to rise in unvaccinated neighborhoods in the city and he wanted to ensure New Yorkers that their public employees were vaccinated or proven safe.

"We're going to keep climbing this ladder and adding additional measures as needed mandates and strong measures, whenever needed to fight the delta variant," the mayor said during a news conference Monday.

A few hours later, California Gov. Gavin Newsom announced that he would place a similar testing mandate for any state employee who can't provide proof of vaccination. The mandate affects 249,000 employees and also provides exemptions for religious or medical reasons.

"California has committed to vaccination verification and or testing on a weekly basis," Newsom said at a news conference.

California's policy will take effect on Aug. 9.

Mathema said the policy will be most effective at swaying unvaccinated employees who were on the fence about getting the shot and needed an incentive to do so.

In this case, time spent on taking a COVID-19 test, submitting the paperwork to a boss and getting their OK week after week would take its toll, Mathema said.

"There will certainly be some people who find the constant testing inconvenient," he said.

Dr. John Brownstein, an epidemiologist at Boston Children's Hospital and an ABC News contributor, said the testing requirement will put extra pressure on an unvaccinated employee to get their shot.

"They’ll have to quarantine and put themselves out of two weeks of work," he said.

Brownstein predicted that more states will follow New York City and California's lead and there appears to be momentum at the federal level. President Joe Biden is expected to announce Thursday that all federal employees show proof of vaccination or submit to regular testing, ABC News has learned.

Brownstein added that some businesses have begun to implement rules that provide more benefits for customers. Some cruise ships, he noted, restrict their non-vaccinated passengers from the more popular dining areas and attractions.

"It’s a hybrid carrot and stick situation. You’re giving benefits to people who are vaccinated and punishing people who aren't," he said.

Mathema warned that there are likely to be a number of public employees who will submit to the weekly testing rather than get their shots. He reiterated that elected officials and businesses that implement a testing mandate for the unvaccinated needed to supplement their policy with a focused educational plan.

"I do believe this needs to be met with outreach, strong outreach and consistent outreach," Mathema said. "We do need to be tactful, show empathy and address real issues that are out there: people's concerns over the vaccine."

Anyone who needs help scheduling a free vaccine appointment can log onto vaccines.gov.

ABC News' Aaron Katersky contributed to this report.