Employers, emboldened by news that at least one vaccine is approved by the Food and Drug Administration, and looking for ways to encourage vaccinations amid a surge in the delta variant, have increasingly embraced new tools to get more shots into arms, in addition to mandates.

A number of new job posts contain notice that new employees need to be vaccinated, according to a recent article in DealBook. Data released by Indeed, the job site, showed such listings have grown 90% between early July and August, during a particularly large spike in the delta variant. The move has been met with mixed results, especially due to the labor shortage, and a number of antivax job sites have sprung up in response.

Other companies are exploring ways to add a health surcharge to employees who aren’t getting vaccinated, arguing that no jabs means higher healthcare costs for the company at large. Delta Air Lines became one of the more prominent companies levying this fee, when it announced $200-a-month insurance surcharges for unvaccinated employees. A recent HR Dive article found that of the companies considering such a move, many expect to charge $20 to 25 a paycheck, with extreme examples tipping toward $50 per paycheck.

The strategy does come with some difficult implementation issues, including deciding how long to give employees to get vaccinated before instituting the penalty, and critics have argued the strategy may be both ineffective for many reasons, including the ability to opt out of employee healthcare programs, and the fact they are proportionately harmful to low-income workers.