With the emergency use authorization (EUA) of the Janssen Pharmaceuticals/Johnson & Johnson COVID-19 vaccine, three vaccines are now available in the U.S. to prevent SARS-CoV-2 hospitalizations and death. The newest vaccine, given as a single dose and stable at refrigeration temperatures for at least three months, presents far fewer logistical challenges in getting doses to consumers.

All of the three current U.S. vaccines use a single protein from SARS-CoV-2 to enable the body to react to the whole virus. The Pfizer/BioNTech and Moderna vaccines are messenger RNA vaccines that use a synthetic version of part of the SARS-CoV-2 genome to teach our cells to replicate the spike protein found on the surface of the virus. This copy of the protein then stimulates the immune system to produce antibodies and other cells that will recognize the actual virus if it is encountered in the future.

The new vaccine employs a different mechanism to produce the same result. A human adenovirus, modified to disable its ability to multiply and infect, acts as a “vector” to carry a gene from the spike protein into our own cells, where the protein is replicated and activates the immune system as above.

(The Oxford/AstraZeneca COVID-19 vaccine, currently in use in the UK, Canada, and Australia, is also a vector vaccine. Granted emergency use listing by the World Health Organization, that vaccine is being rolled out via the multinational COVAX initiative for use in 142 low- and middle-income countries.)

Comparative effectiveness of the new vaccine.

All three vaccines in use in the United States are more effective than the average annual influenza vaccine. As with influenza, the vaccine may not always prevent illness, but should ameliorate the severity of disease if infection occurs despite vaccination.

Johnson & Johnson’s COVID-19 vaccine seems, at first glance, less effective than the Pfizer and Moderna vaccines. A single dose was found to be 66% effective in preventing moderate to severe/critical COVID-19 infection after 28 days, 85% effective in preventing severe/critical illness after 28 days. However, it was 100% effective in protecting against death everywhere it was tested, including in Johnson & Johnson’s trials in South Africa, when the variant virus was present. (The Pfizer and Moderna vaccines were trialed only in the U.S., and prior to the arrival of variants.)

There were zero hospitalizations and zero deaths during clinical trials for all three vaccines. Vaccination data from Israel, released in January, produced results similar to those in the clinical trials: of more than 700,000 people vaccinated, only 16 (less than 0.002%) were hospitalized, and no one died.

Equal effectiveness in preventing deaths from COVID-19.

For the most critical outcome—preventing deaths from COVID-19—all three vaccines are equally effective. And Johnson & Johnson’s 85% effectiveness against critical illness compares favorably to the other two vaccines’ 95% overall effectiveness against any symptomatic illness, mild to critical. Once there is widespread vaccination in the U.S., it is this protection against severe illness, hospitalization, and death that will bring the pandemic under control.

Safety.

The Johnson & Johnson vaccine can produce adverse effects that are similar to those from the earlier vaccines: pain at the injection site, fatigue, headache, fever, and muscle and joint pain. After more than 80 million doses of the first two vaccines administered in the U.S., no serious, long-term adverse effects from any of the vaccines have been identified.

Some final notes about where we’re at with COVID-19 vaccination.

  • These vaccines are not interchangeable. For two-dose vaccines, both doses should be from the same manufacturer.
  • More and more evidence suggests that transmission of asymptomatic disease from vaccinated individuals is very unlikely.
  • The more quickly we vaccinate people, the harder it is for new variants to develop and be transmitted. Variants arise more quickly when transmission is more widespread, because repeated replication of the virus is necessary in order for variants to develop.
  • Disparities in vaccine availability continue. State and local leadership need to step up and take responsibility for more equitable distribution. See this STAT news article for a good explanation of the ways in which vaccines intended for underserved communities don’t reach their intended recipients.
  • As the vaccine rollout continues, don’t abandon masking, physical distancing, and avoiding crowds (especially indoors)—not because vaccination is ineffective, but because it is only one of several public health measures that are vital to bringing the continuing crisis under control. The CDC’s new guidance document, “Interim Public Health Recommendations for Fully Vaccinated People,” provides some practical parameters to keep in mind.