Americans have continued working towards getting their COVID-19 vaccinations in the ongoing battle to keep the pandemic under control and get life back to normal in the United States, but questions still remain over whether the goal of 70% of the population having protection against the virus will still be enough to achieve herd immunity and guarantee a return to the status quo.

The latest data from the CDC shows 40.2% of the U.S. population has been fully vaccinated against the virus, including 74.5% of those age 65 and over and 50.9% of those over the age of 19. A new poll from the Kaiser Family Foundation also revealed promising results that indicate 70% of the adult population could become fully vaccinated by this summer, with increases in the numbers of both Latino adults and those without college degrees when it came to vaccinations. According to the New York Times, 62 percent of those surveyed had also received at least one dose of a vaccine, an increase from numbers who had done so in April.

The study findings that 70% could be vaccinated by summer is promising, especially after Dr. Anthony Fauci, the nation’s leading expert on infectious diseases, previously said that in order to reach a level of “herd immunity,” which would allow life to return completely back to normal, 70-85% of the U.S. population would need to be vaccinated. If that goal can be reached by the summer, it would mean life truly could return to normal—though the question still remains regarding how long that would last, with vaccine efficacy currently only studied through a six-month period post dosage.

Fauci told Axios earlier this month that a vaccine booster shot would likely need to be given to Americans within a year of their initial jabs, stating that the vaccine was not meant to give lifelong protection. Similar to the Flu Shot, it would likely need to be administered more than just the one or two times it has already been.

Currently, while experts say boosters are likely going to be needed at some point, it’s still unclear about when, because more research is needed to determine how long immunity from the virus lasts in those who have been vaccinated.

“We’ll have to see where this all interacts. Is it possible we’re going to need a booster at some point? Yes. Is it probably? Yes. Do we know exactly when? No,” Dr. Peter Marks, director of the US Food and Drug Administration’s Center for Biologics Evaluation and Research said this week (via CNN). “But if I had to look at my crystal ball, it’s probably not sooner, hopefully, than a year after being vaccinated, for the average adult.”

Regardless of whether boosters will be needed or not though, incentives to get those who have been hesitant to receive their shots previously are continuing to grow, as both companies and actual states start trying to give people more reasons to get their shots—beyond their health.

Initially, there were offers of free donuts and beers to those who could give proof of vaccination, but those have since evolved with more lucrative deals.

Kroger stores have started a campaign to get people vaccinated by offering a $1 million prize to five lucky recipients, as well as a year of free groceries to an additional 50 customers. CVS is also starting a #OneStepCloser sweepstakes in June, with 125 $500 cash prizes, five $5,000 cash prizes, 100 seven-day cruises, VIP tickets to Super Bowl LVI and the NCAA Final Four, a four-day trip to Bermuda and several other prizes.

California, Ohio and Colorado have also started contests in their states to give away cash prizes for those who receive their shots.

vials of Comirnaty vaccine by Pfizer-BioNTech against Covid-19
This picture taken on May 13, 2021, shows vials of Comirnaty vaccine by Pfizer-BioNTech against Covid-19 in a fridge at the Baleone vaccine centre in Ajaccio on the French Mediterranean island of Corsica. - Vaccination is opened for people over 18 years old since early May in Corsica. The island has the highest vaccination rate in France. PASCAL POCHARD-CASABIANCA/AFP via Getty Images