Johnson & Johnson's one-shot Covid-19 vaccine received US authorization on Saturday and will start being administered to Americans within days.
The following is how it fits into the vaccination effort with the two other authorized immunizations from Pfizer Inc/BioNTech SE and Moderna Inc.
Is J&J's Vaccine As Effective As The Other Two?
The Pfizer/BioNTech and Moderna vaccines, which both use new messenger RNA technology, showed efficacy of around 95% percent in preventing illness in large trials, while J&J's showed efficacy of around 66%.
However, the trials had important differences, making comparison difficult. Pfizer and Moderna focused on efficacy against mild-to-moderate sickness, while J&J's trial looked for efficacy against moderate-to-severe Covid-19.
J&J's trial was conducted later and included significant numbers of participants in regions where highly transmissible new variants of the virus were circulating, potentially subjecting its shot to a more rigorous test.
Importantly, J&J's vaccine was about as effective against severe illness and hospitalization as the other vaccines and, like the others, was 100% effective in preventing Covid-19-related death in the trial.
All three vaccines have a similar range of short-lived side effects, including fatigue, aches, injection site soreness, nausea and fever, mostly mild-to-moderate.
If J&J's Shot Is Less Effective, Why Should I Get It?
J&J's vaccine is a single shot. Pfizer/BioNTech and Moderna vaccines each require two shots three or four weeks apart.
J&J's shot is extremely effective at preventing people exposed to Covid-19 from getting severely ill or dying, as well as offering protection against milder cases.
"These vaccines are the path to getting your life back," said Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security. "These are vaccines you should not hesitate to get when offered."
J&J's vaccine is one of the few that has been tested in clinical trails against the worrisome virus variant first discovered in South Africa. It demonstrated an ability to provide protection against severe disease and death even for those infected with that variant. Pfizer and Moderna have only tested their vaccines against the variant in the lab and believe they will remain protective.
Do I Have A Choice Of Vaccine?
Experts say that for the next couple of months vaccine supplies will be too scarce for healthcare providers to offer a choice. Most vaccination sites will receive only one of the three vaccines at any given time.
Patients who prefer a specific vaccine can ask healthcare providers which one they have on hand. Later in the year, greater availability of shots could result in more patient choice, but health experts strongly advise taking whichever vaccine you can get.
How Many Doses Of J&J's New Shot Will Be Available?
J&J said it expects to ship nearly 4 million doses in the first week, and shipments could begin late Sunday or early Monday.
J&J expects to deliver a total of 20 million shots by the end of March and as many as 100 million doses by mid-year.
The federal government, through distributor McKesson Corp, will ship J&J's shots to states and territories around the United States. It will also deliver them to select pharmacies and community health centers to make sure they reach underserved populations.
Between J&J, Pfizer/BioNTech and Moderna, the United States is on track to receive 240 million doses by the end of March, enough to fully inoculate 130 million Americans. The drugmakers have agreed to send 700 million doses of their vaccines by the end of July, more than enough to vaccinate all Americans.