The Biden ad­min­is­tra­tion’s goal of kick­ing off its boost­er shot dri­ve for the en­tire US pop­u­la­tion this week is not quite go­ing as planned.

First, Pfiz­er ap­plied for ap­proval of a sup­ple­men­tal ap­pli­ca­tion for the boost­er shots, but since last Fri­day’s ad­comm re­view­ing them, the plan has de­volved in­to an EUA, which the FDA is­sued late Wednes­day evening.

The pop­u­la­tion that is now el­i­gi­ble for the boost­er, six months af­ter re­ceiv­ing the first pair of Pfiz­er-BioN­Tech vac­cines, al­so nar­rowed from what Pfiz­er ap­plied for (every­one who’s el­i­gi­ble for the ini­tial Pfiz­er shots) to just those who are 65 or old­er, or at high-risk of a Covid in­fec­tion, in­clud­ing health care work­ers and oth­ers with oc­cu­pa­tion­al haz­ards.

“Af­ter con­sid­er­ing the to­tal­i­ty of the avail­able sci­en­tif­ic ev­i­dence and the de­lib­er­a­tions of our ad­vi­so­ry com­mit­tee of in­de­pen­dent, ex­ter­nal ex­perts, the FDA amend­ed the EUA for the Pfiz­er-BioN­Tech COVID-19 Vac­cine to al­low for a boost­er dose in cer­tain pop­u­la­tions such as health care work­ers, teach­ers and day care staff, gro­cery work­ers and those in home­less shel­ters or pris­ons, among oth­ers,” act­ing FDA com­mis­sion­er Janet Wood­cock said in a state­ment.

The agency said it’s re­ly­ing on an analy­sis from Pfiz­er show­ing that over the last two months, the in­ci­dence of Covid-19 was high­er among the tri­al par­tic­i­pants who com­plet­ed their pri­ma­ry vac­cine se­ries ear­li­er, com­pared to par­tic­i­pants who com­plet­ed it lat­er.

“The FDA de­ter­mined that the rate of break­through COVID-19 re­port­ed dur­ing this time pe­ri­od trans­lates to a mod­est de­crease in the ef­fi­ca­cy of the vac­cine among those vac­ci­nat­ed ear­li­er,” the agency said.

And for those re­ceiv­ing the boost­ers due to high risk of se­vere Covid-19 and in­sti­tu­tion­al or oc­cu­pa­tion­al ex­po­sure risk, they must be adult, 18 through 64 years of age, which ex­cludes the 12-18 age group for which the vac­cine is ei­ther au­tho­rized or ap­proved.

The EUA fol­lows close de­bate and dis­agree­ment among vac­cine ex­perts ad­vis­ing the FDA, and the FDA’s own in­ter­nal vac­cine ex­perts.

The FDA’s ad­comm on vac­cines round­ly re­ject­ed the Pfiz­er/BioN­Tech boost­er shots for all in­di­vid­u­als old­er than 16 by a 16-2 vote Fri­day af­ter­noon. Soon af­ter, how­ev­er, the agency posed a new ques­tion to com­mit­tee mem­bers on lim­it­ing boost­er use to the 65-and-old­er pop­u­la­tion and in­di­vid­u­als at high risk of dis­ease due to oc­cu­pa­tion­al ex­po­sure or co­mor­bidi­ties (which is what the agency in­evitably went with).

That ques­tion, com­ing rough­ly 45 min­utes af­ter the first, passed through the ad­comm with a unan­i­mous 18-0 vote. This vote cen­tered on an EUA — not the sBLA for which Pfiz­er had ap­plied. While CBER head Pe­ter Marks al­lowed the ad­di­tion­al ques­tion and vote, which were not on the agen­da, top CBER of­fi­cial Mar­i­on Gru­ber ques­tioned the move. Gru­ber and her deputy Phil Krause are re­tir­ing soon, at least in part due to the ad­min­is­tra­tion’s over-step­ping its bounds on the boost­er de­ci­sion, they wrote in the Lancet last week.

Krause al­so ques­tioned Pfiz­er at the ad­comm on cer­tain sta­tis­ti­cal dis­crep­an­cies that showed its vac­cine’s ef­fi­ca­cy plum­met­ed to about 60%, where­as his analy­sis through a dif­fer­ent math­e­mat­i­cal process us­ing cas­es per per­son-years re­sult­ed in 93% ef­fi­ca­cy. These dis­parate fig­ures, Krause said, came from the same num­ber of cas­es in a study by Kaiser Per­ma­nente.

The CDC’s ACIP com­mit­tee will meet Thurs­day to dis­cuss its rec­om­men­da­tion on who specif­i­cal­ly should ac­cess boost­ers.

Steve Holtzman was awoken by a 1 a.m. call from a doctor at Duke University asking if he could put some pigs on a plane and fly them from Ohio to North Carolina that day. A motorcyclist had gotten into a horrific crash, the doctor explained. He believed the pigs’ livers, sutured onto the patient’s skin like an external filter, might be able to tide the young man over until a donor liver became available.

David Livingston, the Dana-Farber/Harvard Med scientist who helped shine a light on some of the key molecular drivers of breast and ovarian cancer, died unexpectedly last Sunday.

One of the senior leaders at Dana-Farber during his nearly half century of work there, Livingston was credited with shedding light on the genes that regulate cell growth, with insights into inherited BRCA1 and BRCA2 mutations that helped lay the scientific foundation for targeted therapies and earlier detection that have transformed the field.

Pfizer will present its case to the FDA’s vaccine adcomm next week, seeking authorization for a lower-dose version of its Covid-19 vaccine for kids ages 5 through 12, which the Biden administration said will likely begin rolling out early next month.

Two primary doses of the 10 µg vaccine (the dose for those ages 12 and up is 30 μg) given 3 weeks apart in this group of children “have shown a favorable safety and tolerability profile, robust immune responses against all variants of concern including Delta, and vaccine efficacy of 90.7% against laboratory-confirmed symptomatic COVID-19,” the company said in briefing documents ahead of next Tuesday’s meeting of the FDA’s Vaccines and Related Biological Products Advisory Committee.

The FDA late Wednesday signed off on authorizing the use of heterologous — or what FDA calls a “mix and match” of a primary vaccine series and different booster doses — for all currently available Covid-19 vaccines, in addition to separately authorizing Moderna and J&J boosters.

On the mix-and-match approach, which FDA officials insisted isn’t too confusing in a press conference, the agency offered the example of an 18-year-old who received the J&J shot at least two months ago and may now receive a single booster of the J&J, a half dose of the Moderna, or the Pfizer-BioNTech booster.