In a move that came as a surprise to many—including US federal and local administration officials, scientists, and members of the public—on May 13, 2021, the US Centres for Disease Control and Prevention (CDC) changed its recommendations on mask use. Individuals who are fully vaccinated are now allowed to resume activities they did before the COVID-19 pandemic and to socially interact without wearing masks or physically distancing, including indoors, with the exception of on public transport, in health-care facilities, and in settings where different federal, state, or local regulations on mask use apply. No restrictions are in place on the number of people gathering. By contrast, individuals who are not fully vaccinated must continue to follow the previous guidelines—ie, wear a mask, keep a 6-foot (1·8 m) distance from others, and avoid crowds or poorly ventilated places.This relaxation has been widely celebrated, with US President Joe Biden calling it a milestone in the fight against COVID-19, but it has also sparked debate. On paper, the new recommendations are logical. Real-world data confirm published interim trial data that vaccines approved in the USA prevent serious disease and death and further indicate that they reduce the risk of transmission of SARS-CoV-2. Therefore, when not wearing masks, fully vaccinated individuals are at low risk of both getting and spreading COVID-19. However, there are some considerations to be made.First, the new guidelines create a tiered society based on vaccination status, with those who are not fully vaccinated having reduced liberties compared with fully vaccinated people. Indeed, part of the rationale behind the change in guidelines is the hope that reduced restrictions will incentivise vaccine-hesitant people to get vaccinated. Although this strategy might work in the case of individuals who do not plan to get vaccinated because they are not concerned about getting infected with SARS-CoV-2 (eg, young people, who rarely develop severe symptoms), it is unlikely to change the attitudes of those who do not believe in the efficacy of the vaccine, who fear its side-effects, who cannot afford to take time off work to get it, or who are unaware that the vaccine is free.Second, as it is unclear whether and how the new recommendations will be enforced, it seems conceivable that people who are against wearing masks in the first place will take the chance to stop wearing them altogether, regardless of their vaccination status. If such an attitude became widespread, it could lead to new outbreaks and increases in the numbers of COVID-19 cases, hospitalisations, and deaths, particularly in areas where vaccination rates are currently low but transmission is ongoing. Furthermore, it would put at increased risk individuals who cannot be vaccinated (eg, for health reasons) and those who even when vaccinated might not be fully protected (eg, individuals on immunosuppressive drug regimens).Finally, at the time of the change in CDC recommendations, about 36% of US citizens had been fully vaccinated. In the global landscape, that is an impressive achievement, but it is still far from the proportion of vaccinated population thought to be necessary for herd immunity (60–70%). Cases of infection with the SARS-CoV-2 variant first identified in India, B.1.617, have been reported in the USA, and although insufficient data are available on its transmissibility and immune evasion potential, the rapid increase in infections with this variant in other countries (such as India itself and the UK) suggests it might be highly transmissible. If this is indeed the case, with the majority of the US population not fully protected, the risk of a new spike in infections should not be underestimated.All in all, the decision to grant different degrees of liberty to different subsets of the population appears premature. Waiting a few additional weeks would have allowed for a substantially larger fraction of the population to be immunised, and perhaps granting a few more liberties to all—such as no masks in outdoor spaces, where a minority of infections occur, but continued use of masks and physical distancing in indoor settings—would have been easier to control and, more importantly, fairer.