The prospect of a third vaccine arrives the same week the United States marked the grim milestone of 500,000 deaths and at a crucial moment in the pandemic. After weeks of declining new cases, the downward trend has stalled — a change that makes many experts uneasy that officials are relaxing restrictions and people are letting their guard down just when variants capable of spreading faster or slipping by some aspects of immunity are poised to take off.
Adding another vaccine will help bolster the nation’s limited supply of the two authorized shots, one made jointly by Pfizer and its German biotech partner BioNTech and the other from Moderna. It should help accelerate the vaccination campaign, although the initial impact of the Johnson & Johnson vaccine is expected to be modest as the company ramps up manufacturing over the next month, with the first 20 million doses expected to be delivered by the end of March.
“There are limited options to control the virus,” said Gregory A. Poland, director of the Vaccine Research Group at the Mayo Clinic, who made a presentation to the FDA advisers as part of the Johnson & Johnson presentation and is a paid expert consultant to the company. “We need vaccines that are effective and well-tolerated, and — importantly — ones that are simple to deploy.”
Poland argued that a one-dose vaccine could speed up and simplify the effort to reach individual and herd immunity, making mass immunization campaigns that could end the pandemic more logistically feasible.
Johnson & Johnson applied to the FDA for emergency use authorization in early February, submitting clinical trial data involving 44,000 participants in eight countries. The data showed that the vaccine was 72 percent effective in preventing cases of moderate to severe covid-19 in the United States, where variants of concern have only recently begun to be detected.
In South Africa, where a variant capable of evading some parts of immunity became dominant late last year, it was 64 percent effective against moderate to severe illness. Across countries, it was completely effective in preventing hospitalization and deaths a month after study participants received the shot.
During the presentation to FDA advisers, company officials underscored the strong protection the vaccine provided against severe bouts of illness, the outcome that is of greatest concern. The vaccine was 85 percent protective against severe cases of covid-19, the disease caused by the coronavirus, and that protection was consistent even in regions of the world where concerning variants have arisen.
Compared with the first two vaccines, Johnson & Johnson’s one-shot vaccine was tested during a more complicated phase of the pandemic, when a variant capable of slipping by some immunity had emerged.
The United States backed the development of the vaccine and has ordered 100 million doses, through $1.5 billion in contracts. Federal health officials have said 3 million to 4 million doses could be shipped next week, if the vaccine is authorized, with 20 million doses total expected in March. The remaining doses are scheduled to be delivered by the end of June.
“During the last two months, we have all seen it is critically important to manufacture and distribute vaccines quickly and efficiently. And Janssen’s vaccine offers logistical and practical advantages to help simplify the distribution and expand vaccine access,” said Johan Van Hoof, global therapeutic area head of vaccines for Janssen, the Johnson & Johnson division that developed the vaccine.
The first coronavirus vaccines in the United States were authorized in December. They are being distributed nationally in an unprecedented drive to stem covid-19.
The advisory committee, which includes pediatricians, infectious-disease doctors and biostatisticians, heard presentations by the FDA, the Centers for Disease Control and Prevention and Johnson & Johnson. The stage was set for the committee’s positive recommendation on the vaccine by the FDA’s upbeat assessment, issued Wednesday.
The efficacy rate was lower, about 42 percent, in preventing moderate to severe illness in adults 60 and older who had diabetes, obesity or other chronic medical conditions. But the FDA said there was a high degree of statistical uncertainty regarding the data, which might reflect a smaller number of participants in that category.
The FDA, in deciding whether to clear a product, usually follows the nonbinding advice of its outside experts. An emergency use authorization is not a full approval. It is a temporary clearance that can be granted relatively quickly during a public health emergency and requires a lower level of evidence. But the FDA decided last year to use criteria for coronavirus vaccines that was nearly as rigorous as what is used for approvals.
All the vaccines in late-stage development work by introducing the immune system to versions of the spike protein that dots the outside of the coronavirus. But the Johnson & Johnson vaccine adds a different technology to the mix, one that takes a more traditional approach than the Pfizer-BioNTech and Moderna products.
The new vaccine uses a harmless cold virus that has been genetically tweaked so that it cannot make copies of itself. That cold virus acts as a vector to deliver a gene encoding the spike protein to cells. The Pfizer-BioNTech and Moderna vaccines, in contrast, deliver a strip of genetic material called messenger RNA that carries the instructions to build the spiky protein found on the outside of the virus.
In all three vaccines, cells follow genetic instructions to construct the spike, and the immune system learns to recognize the real thing from these replicas.
