NVAX Novavax Inc

By Taylor Umlauf and Peter Loftus 

Seven coronavirus vaccines are rolling out across six continents to slow the global pandemic, and more are in late-stage testing. The shots use different technologies to help people mount the molecular defenses that can fend off Covid-19.

Vaccines from Moderna Inc. and Pfizer Inc. and its German partner BioNTech SE mobilize immune defenses using genetic molecules known as messenger RNA packaged in fat envelopes, while AstraZeneca Inc.'s vaccine and Russia's Sputnik V shot deliver immune prompts with the help of common, harmless viruses. A Beijing-based drug-development unit of China National Pharmaceutical Group Co., known more commonly as Sinopharm, relies on the traditional vaccine approach: prompting immune defenses against a dangerous virus by injecting a defanged version of the pathogen. Another vaccine, now in late-stage testing from U.S.-based Novavax Inc., relies on a fourth technology.

The vaccines appeared to have different levels of effectiveness during testing, and different side effect risks. The following explains how each of these vaccines works.

Genetic-Code

The mRNA technology behind the Pfizer and Moderna vaccines -- the two currently in use in the U.S. -- had never been approved before the pandemic. Messenger RNA carries to cells the genetic instructions for making proteins. The mRNA vaccines ferry orders, engineered in a lab, for making a harmless version of the protein from the novel coronavirus, prompting cells to make the protein and the immune system to mobilize molecular defenses that can spring into action if exposed to the real coronavirus.

Among the Covid-19 vaccines currently in use, mRNA vaccines have had the highest efficacy rates during late-stage testing.

Moderna

-- Available in: U.S., Canada, parts of Europe, Israel

-- Doses: 2

-- Efficacy: 94%

-- Most common side effects: Injection-site pain, fatigue, headache, muscle pain

Pfizer

-- Available in: U.S., Canada, Mexico, U.K., parts of Europe and the Middle East, Ecuador and Singapore

-- Doses: 2

-- Efficacy: 95%

-- Most common side effects: Injection-site pain, fatigue, headache, muscle pain

Virus-Based

Two of China's vaccines rely on the traditional vaccine method, much like the technology behind shots for the flu or polio. These traditional vaccines use a killed or weakened form of the targeted virus to generate an immune response that can protect against the pathogen. So far, studies on the effectiveness of Covid-19 vaccines using the traditional technology have shown them to have lower efficacy rates than other shots with late-stage study results.

China's state-owned Sinopharm

-- Available in: China, Bahrain, Serbia, U.A.E., Seychelles

-- Doses: 2

-- Efficacy: 79%, interim Phase 3 results

-- Most common side effects: Injection-site pain, headache, muscle pain, fever

Sinovac Biotech Ltd.

-- Available in: China, Brazil, Indonesia, Turkey

-- Doses: 2

-- Efficacy: 50% (based on clinical trials in Brazil)

-- Most common side effects: Unknown

Viral Vectors

Several vaccines use what is known as a viral-vector approach, a reference to how the shots deliver immune-mobilization orders. The technology is behind some relatively new vaccines to protect against another deadly infectious disease, Ebola.

Among the viral-vector Covid-19 vaccines are AstraZeneca's, developed with the University of Oxford and in use in the U.K. and across Europe; Russia's Sputnik V; a vaccine from China's CanSino Biologics Inc., working with the Chinese military. The shots use a modified virus -- like the virus responsible for common colds -- to carry genetic instructions teaching cells to make a protein from the coronavirus.

A fourth viral-vector vaccine, from Johnson & Johnson, is in late-stage testing and could be authorized for use in the U.S. as early as February.

AstraZeneca

-- Available in: U.K.

-- Doses: 2

-- Efficacy: 62% (with two doses)

-- Most common side effects: Unknown

Johnson & Johnson

-- Not yet approved for distribution

-- Doses: 1 or 2, pending outcome of clinical trials

-- Efficacy: 66% (based on results released from a large clinical trial Friday), with 72% in the U.S., 66% in Latin America and 57% in South Africa

-- Most common side effects: Fatigue, headache, muscle pain, injection-site pain

Sputnik V

-- Available in: Russia, Serbia, Argentina

-- Doses: 2 (Russia is also offering to foreign customers who want to speed up vaccinations a one-dose version, Sputnik Light, consisting of the first dose of the regular Sputnik vaccine.)

-- Efficacy: 91.4%, in an interim analysis

-- Most common side effects: Injection-site pain and flu-like symptoms including fever, weakness, fatigue and headache

CanSino Biologics, working with the Chinese military

-- Available in: China

-- Doses: 1

-- Efficacy: Unknown

-- Most common side effects: Unknown

Protein-Based

Researchers designed these vaccines to generate an immune response to the coronavirus by introducing one of its proteins, like the spike protein jutting from its surface. The presence of the protein, or something resembling it, should provoke the immune system to develop defenses against the virus, the researchers say. Covid-19 vaccines based on the technology aren't available yet. Novavax's shot, which is in late-stage testing, could be rolled out in the U.S. in spring or summer if it proves to work safely.

Novavax

-- Not yet approved for distribution

-- Doses: 2

-- Efficacy: 89% effective (based on results released from a late-stage study in the U.K. Thursday), with 49% in South Africa (based on a mid-stage trial)

-- Most common side effects: Injection-site pain, fatigue, headache, muscle ache

Sources: Our World In Data (for distribution locations); World Health Organization (doses)

Write to Peter Loftus at peter.loftus@wsj.com

(END) Dow Jones Newswires

January 29, 2021 17:39 ET (22:39 GMT)

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