Despite questions, ‘train has left the station’ on COVID-19 boosters
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Additional doses of COVID-19 vaccine became available to people in the United States around 8 months after the first vaccine was authorized by the FDA.
In mid-August, the FDA authorized patients with certain immunocompromising conditions to receive a third dose of one of the messenger RNA vaccines manufactured by Pfizer-BioNTech and Moderna, including solid organ transplant recipients and others with an equivalent level of immunocompromise.
The decision was “welcomed with open arms by clinicians and patients,” said Infectious Disease News Editorial Board Member Peter Chin-Hong, MD, professor of medicine and director of the transplant infectious disease program at the University of California, San Francisco.
“Although the lion’s share of hospitalized cases in the U.S. and elsewhere have been in the unvaccinated, transplant and other immunocompromised individuals have a lower chance of responding to vaccines — as measured by antibody response — and most importantly, we have been seeing them get admitted to our hospitals with serious breakthrough infections,” Chin-Hong told Infectious Disease News.
Other announcements about extra doses of COVID-19 vaccine were not met with as much enthusiasm.
White House plan
Driven by the delta variant, the U.S. reported a level of new infections in August not seen since the winter. There were nearly 165,000 new cases of COVID-19 on Aug. 26, according to CDC Director Rochelle P. Walensky, MD, MPH.
Around a week earlier, the Biden administration — despite the fact that the FDA had authorized third doses of COVID-19 vaccine only for immunocompromised people — announced that the U.S. would offer booster doses to all fully vaccinated Americans beginning on Sept. 20.
The plan, as it was announced by heath officials, suggested that people receive a third dose of the Pfizer-BioNTech or Moderna mRNA vaccines beginning 8 months after the date they received their second shot.
“It will be just as easy and convenient to get a booster shot as it is to get a first shot today,” White House COVID-19 response coordinator Jeff Zients said during a White House press briefing.
Officials said people who received the Johnson & Johnson vaccine were also expected to need a booster shot.
Walensky and National Institute of Allergy and Infectious Diseases Director Anthony S. Fauci, MD, described U.S. data that influenced the White House booster plan, including three new MMWR reports.
In one of the reports, data showed a decrease in the overall age-adjusted vaccine effectiveness for adults in the state of New York from 91.7% to 79.8% during a 12-week period from May 3 to July 25 in which the proportion of cases in the region caused by the delta variant increased from less than 2% to over 80%.
However, data also showed that the overall age-adjusted effectiveness against hospitalization among vaccinated adults in the state was “relatively stable” at between 91.9% and 95.3%.
Another report assessed the duration of vaccine effectiveness among 3,089 adults hospitalized in 18 states from March 11 through July 14 and found that, among people who received an mRNA vaccine, effectiveness against COVID-19 hospitalization was 86% (95% CI, 82%-88%) overall and 90% (95% CI, 87%-92%) among adults who are not immunocompromised during the entire surveillance period. Vaccine effectiveness declined from 86% (95% CI, 82%-90%) 2 to 12 weeks after receiving the second dose to 84% (95% CI, 77%-90%) 13 to 24 weeks later.
“These data confirm that while protection against infection may decrease over time, protection against severe disease and hospitalization is currently holding up pretty well,” Walensky said during the briefing.
The analysis also found that vaccine effectiveness against COVID-19 hospitalization among patients with immunocompromising conditions was much lower at 63% (95% CI, 44%-76%).
A third analysis of mRNA vaccine effectiveness showed a decline in vaccine effectiveness among nursing home residents from 74.7% (95% CI, 70%-78.8%) in a period stretching from March through May to 53.1% (95% CI, 49.1%-56.7%) in June and July, when the delta variant predominated.
“This represents a substantial decline in vaccine effectiveness against infection among those who are most vulnerable,” Walensky said.
There was a debate about whether the U.S. data — and data from Israel that showed waning effectiveness of the Pfizer-BioNTech vaccine — was enough for the White House to go ahead with the plan, especially in light of pleas that wealthy countries not offer extra doses while vaccination rates remained low in many lower income countries.
“The question is, What was the line that got crossed that made this recommendation?” Paul A. Offit, MD, director of the Vaccine Education Center at The Children’s Hospital of Philadelphia, said in an interview. “It can’t be waning immunity against asymptomatic infection or mildly symptomatic infection, because that’s too high of a bar, I think, for these vaccines.”
Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security, agreed.
“To me, the threshold for recommending boosters for the general population has to be seen in high rates of breakthrough infections leading to hospitalizations,” Adalja told Infectious Disease News. “Absent that, I don’t see a strong need for a third shot for the general population, and the data that the CDC provided really show that the vaccines are very durable about what matters — serious disease andnhospitalizations.”
Adalja said the authorization of third doses for immunocompromised patients “was driven by clinical data that showed that immunosuppressed populations were comprising a significant proportion of breakthrough hospitalizations, as well as having a higher rate of hospitalizations, for example, in the solid organ transplant population, but I haven’t seen any data like that for the general population that’s been published.”
“The MMWR data show exactly what we’ve been saying from the beginning, that the vaccines are very durable against what matters,” he said. “So, I think when you look at the trajectory of this pandemic, the value of putting third doses into people is much, much, much lower than getting first doses into people.”
‘The haves and have-nots’
The U.S. booster plan took shape just weeks after WHO Director-General Tedros Adhanom Ghebreyesus, PhD, MSc, called for a moratorium on booster shots in wealthy countries until at the least the end of September to improve global vaccine equity.
World health leaders reiterated that appeal with even stronger language after details of the U.S. plan leaked in the media.
“We’re planning to hand out extra life jackets to people who already have life jackets while we’re leaving other people to drown without a single life jacket,” Mike Ryan, MD, MPH, director of WHO’s Health Emergencies Program, said during a press briefing.
Tedros said 10 countries have used 75% of the global COVID-19 vaccine supply, whereas just 2% of people living in low-income countries have been vaccinated. Lower income countries, he said, “have not even been able to vaccinate their health care workers and at-risk communities and are now experiencing large spikes.”
Although he noted that the U.S. is the largest sharer of vaccine doses globally — 115 million doses to 80 countries as of Aug. 18, according to Zients — Tedros reiterated his disapproval of the kind of booster program planned by the Biden administration.
“The divide between the haves and have-nots will only grow larger if manufacturers and leaders prioritize booster shots over supply to low- and middle-income countries,” he said during the briefing. “The virus is evolving and it’s not in the best interest of leaders just to focus on narrow nationalistic goals when we live in an interconnected world and the virus is mutating quickly.”
FDA approval is ‘a milestone’
Amid the debate about booster doses, the FDA issued its full approval of the Pfizer-BioNTech vaccine — a long-awaited decision that could have implications for vaccine mandates and uptake in the U.S., experts said.
“The FDA’s approval of this vaccine is a milestone as we continue to battle the COVID-19 pandemic,” acting FDA Commissioner Janet Woodcock, MD, said in the announcement.
The vaccine, now branded as Comirnaty, received full approval for two doses given 3 weeks apart in anyone aged 16 years or older.
Adalja said the approval could impact vaccine mandates as a condition of employment.
“I think that will be a good thing because this is something that we’re kind of hitting the wall about,” Adalja said. “We think that one way to get vaccines up is for organizations and businesses to realize how important having a vaccinated workforce is to their continuity of operations and to the safety of their workplace. This will hopefully pave the way for this to become a very common practice.”
Offit said the approval could help alleviate some vaccine hesitancy from a psychological standpoint.
“I think some people are saying they don’t want to get the vaccine until it’s fully approved, or they don’t trust that the vaccine has yet been proven to be safe, effective, or yet been proven to be manufactured in a consistent and reliable way,” Offit said. “The approval really is more of a psychological thing than anything else, and that’s not trivial.”
With all the focus on vaccines, Infectious Disease News Editorial Board member Jeanne M. Marrazzo, MD, MPH, director of the division of infectious diseases at the University of Alabama at Birmingham, said she worried that the U.S. was losing its focus on other measures to protect against COVID-19, including masks.
“Which is worrisome because masks offer immediate protection— you don’t need to wait several weeks for protective antibody to be made — don’t care what variant they encounter, and with the delta variant being so contagious, offer another layer of barrier protection even for those already vaccinated,” Marrazzo told Infectious Disease News. “With vaccinated people whose antibody levels are waning — after around 8 months — masks can be particularly important right now as we try to get through the current wave.”
After receiving full approval, Pfizer and BioNTech announced that they were seeking FDA approval for a booster dose of the vaccine for people aged 16 years or older.
‘The train has left the station’
Infectious Disease News Editorial Board Member William Schaffner, MD, said it is difficult to “tease apart” whether the reported reduced protection from COVID-19 vaccines is due to the delta variant or less cautious social behaviors that are exposing people to increased risks for infection.
Regardless of regulatory decisions, Schaffner said patients were already seeking extra doses of vaccine.
“Some patients are out there going to vaccination sites all by themselves and asking for them and getting them, and there are already doctors who are getting all kinds of questions about this,” he told Infectious Disease News. “It’s not so much dangerous, but it certainly indicates that the train has left the station.”
- References:
- Nanduri S, et al. MMWR Morbid Mortal Wkly Rep. 2021;doi:10.15585/mmwr.mm7034e3.
- Rosenberg ES, et al. MMWR Morbid Mortal Wkly Rep. 2021;doi:10.15585/mmwr.mm7034e1.
- Tenforde MW, et al. MMWR Morbid Mortal Wkly Rep. 2021;doi:10.15585/mmwr.mm7034e2.
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