The CDC’s new advisory, letting the fully vaccinated go without masks in most settings, was surprising. The biggest change in the pandemic response and the strongest clue of a return to normalcy came rather abruptly. Was it guided by politics, as some alleged, or by science as the agency insists?

After all, it was only on Tuesday that CDC director Rochelle Walensky had, at a Senate health committee hearing, vehemently defended the Biden administration’s masking and social distancing policies. [https://www.washingtonpost.com/politics/biden-masks-vaccinated/2021/05/15/914a18c6-b4d5-11eb-a980-a60af976ed44_story.html] She had then ruled out any relaxation, citing the fact that only a third of the country was fully vaccinated and also that Covid-19 was still raging in many parts of the world. As the CDC publicly announced the revised guidance only two days later, on Thursday, there was disbelief and criticism in some quarters. President Biden’s rivals saw an attempt to infuse some good news in a bad week of troubles with gas pipelines, Israel-Palestine conflict and inflation numbers.

The CDC, of course, maintains that its decision was not influenced by any factor other than scientific inputs. The agency had taken the call on the basis of new data, Walensky said in defense on Sunday. [https://abcnews.go.com/Politics/mask-guidance-grant-permission-widespread-mask-removal-walensky/story?id=77713729] When the new recommendation was announced, she had cited two new studies which showed that it was rare for the vaccinated to be infected, and even rarer for them to transmit infection and, secondly, that the current vaccines provide effective protection against all known variants of the virus. [https://www.nytimes.com/2021/05/14/health/cdc-masks-vaccines-variants.html]

For example, the CDC Friday released the findings of an interim study [https://www.cdc.gov/mmwr/volumes/70/wr/mm7020e2.htm?s_cid=mm7020e2_w] that Pfizer-BioNTech and Moderna vaccines are 94 percent effective in preventing symptomatic Covid-19 in those who were fully vaccinated, and 82 percent effective even in those only partly vaccinated. [https://www.cnbc.com/2021/04/28/cdc-pfizer-moderna-vaccines-94-percent-effective-at-preventing-elderly-hospitalizations.html]

One explanation of the too quick about-turn is that Walensky had made the decision on Monday, a day before the hearing, and scientist at the agency were scrutinizing last details before the formal announcement, and in the meanwhile, CDC chief merely stuck to the script before the committee. [https://www.washingtonpost.com/health/2021/05/16/cdc-mask-vaccinated-change/]

Latest guidance from CDC:
https://www.cdc.gov/coronavirus/2019-ncov/vaccines/fully-vaccinated.html