{"id":270971,"date":"2020-10-07T00:51:32","date_gmt":"2020-10-07T04:51:32","guid":{"rendered":"https:\/\/canadianinquirer.net\/v1\/?p=270971"},"modified":"2020-10-07T00:51:32","modified_gmt":"2020-10-07T04:51:32","slug":"what-does-covid-19-vaccine-efficacy-mean","status":"publish","type":"post","link":"https:\/\/canadianinquirer.net\/v1\/2020\/10\/07\/what-does-covid-19-vaccine-efficacy-mean\/","title":{"rendered":"What does COVID-19 vaccine efficacy mean?"},"content":{"rendered":"
\"\"<\/a>
The FDA setting a minimum recommendation for efficacy doesn\u2019t mean vaccines couldn\u2019t perform better. (File photo: National Cancer Institute\/Unsplash)<\/figcaption><\/figure>\n

Predicting how a vaccine will work in the real world is tricky
\n<\/strong><\/p>\n

With several vaccines against COVID-19 in late-phase testing, the business of measuring efficacy is front and center.<\/p>\n

Determining the efficacy, or how well a vaccine works in a randomized, controlled trial, gives a sense of how much a vaccine could help alleviate the suffering caused by COVID-19. The U.S. Food and Drug Administration recommends vaccines tested against COVID-19 reach\u00a0an efficacy of 50 percent, at minimum<\/a>. That means at least a 50 percent reduction in cases of COVID-19 disease in those who are vaccinated compared with those who receive the placebo.<\/p>\n

Johnson & Johnson, Moderna, Pfizer and AstraZeneca have each begun phase III trials of their vaccines in the United States. These late-phase trials, which will each assess safety and efficacy in tens of thousands of people, randomly assign some participants to receive vaccinations and others a placebo. The companies and the U.S. government,\u00a0working together<\/a>\u00a0as part of Operation Warp Speed, have set a goal of having initial doses of a vaccine available by January 2021 (SN: 7\/10\/20<\/em>). It won\u2019t be clear how well any of these vaccines do their job until the companies report full results from those trials; some preliminary results may come out as early as October.<\/p>\n

The FDA setting a minimum recommendation for efficacy doesn\u2019t mean vaccines couldn\u2019t perform better. The benchmark is also a reminder that COVID-19 vaccine development is in its early days. If the first vaccines made available only meet the minimum, they may be replaced by others that prove to protect more people. But with more than 1 million deaths from COVID-19 worldwide \u2014 and U.S. deaths surpassing 200,000 \u2014 the urgency in finding a vaccine that safely helps at least some people is at the forefront.<\/p>\n

\u201cYou want to set the bar [for efficacy] high enough so that it is clinically and epidemiologically significant, but low enough that a \u2018good enough\u2019 vaccine can be licensed until something better comes along,\u201d says Kawsar Talaat, a vaccine researcher at the Johns Hopkins Bloomberg School of Public Health.<\/p>\n

The World Health Organization has also set a minimum target of 50 percent efficacy for vaccines tested against COVID-19, but its \u201cpreferred efficacy\u201d is at least 70 percent<\/a>.<\/p>\n

Efficacy specifically applies to how a vaccine works in a clinical trial. For the four vaccine candidates now in phase III trials in the United States, the primary goal is not necessarily to stop an infection but to prevent a person from experiencing symptoms of COVID-19 or, in Johnson & Johnson\u2019s case, to guard against moderate to severe illness. Researchers will count cases of symptomatic COVID-19 in the vaccinated group and in the placebo group (who get injections of saline, for example) and calculate how much of a reduction there was with vaccination.<\/p>\n

\u201cAt least with the first generation of vaccines,\u201d Talaat says, \u201cwhat we\u2019re really trying to do is prevent severe disease and hospitalization and death.\u201d<\/p>\n

A vaccine that prevents people from developing symptoms may not stop them from becoming infected and passing the virus to others. If such a vaccine gets approved, what the vaccine does and doesn\u2019t do would need to be communicated very clearly, says Maria Bottazzi, a vaccinologist at the Baylor College of Medicine in Houston. People would still need to wear masks and practice social distancing to help keep the virus from spreading, she says.<\/p>\n

The efficacy results won\u2019t be the final word on how effective the vaccine is in the real world. That\u2019s one reason \u201cwhy it\u2019s always a good idea to have a more diverse population in your trials,\u201d says Saad Omer, a vaccine researcher at Yale University. That way, researchers can gather data on how the vaccine works for different people in a variety of scenarios.<\/p>\n

Studies of other vaccines in which a trial took place in different locations have reported different results based on the incidence of disease in those areas; some vaccines haven\u2019t worked as well in populations where the risk of exposure is higher. In this pandemic, Black and Latino Americans are disproportionately represented in the essential jobs that can\u2019t be done at home,\u00a0putting them at risk for more exposures<\/a>\u00a0to the coronavirus (SN: 7\/2\/20<\/em>).<\/p>\n

A person\u2019s age also affects how well a vaccine will work. Our immune system \u201cages as we age too,\u201d says Bottazzi. When older adults get the flu vaccine, for example, the shot doesn\u2019t elicit as strong an immune response as it does in younger adults. In the United States, adults ages 65 and older can get specially formulated flu vaccines that create a stronger immune response and better protection for this age group.<\/p>\n

For the COVID-19 vaccine trials, the FDA has strongly encouraged \u201cenrollment of populations most affected by COVID-19, specifically racial and ethnic minorities.\u201d The agency also states that the phase III trials should include enough older adults and people with certain underlying medical conditions, two groups at increased risk for COVID-19, to be able to evaluate efficacy for them.<\/p>\n

How well the first COVID-19 vaccines work, and for whom, will influence who is initially prioritized to receive the vaccine. The Advisory Committee on Immunization Practices of the U.S. Centers for Disease Control and Prevention issues guidance on the use of vaccines in the general population. To recommend a COVID-19 vaccine for older adults, for example, there has to be data to show that it works for them.<\/p>\n

There are other COVID-19 vaccines in development and testing; some aren\u2019t very far behind the front runners. Even if one or more of the vaccines now in phase III trials gets the green light, \u201cthe story wouldn\u2019t be over,\u201d says Omer. \u201cIt would be the end of the beginning.\u201d<\/p>\n

Vaccine matchup<\/h3>\n

The next testing hurdle for the initial COVID-19 vaccines in development is to determine efficacy, or how they perform in a clinical trial. The U.S. Food and Drug Administration recommends COVID-19 vaccines have an efficacy \u2014 measured by the reduction in cases of COVID-19 disease among those vaccinated versus those not \u2014 of at least 50 percent. How a vaccine performs once it\u2019s used in the wider world is called effectiveness. See how the minimum goal for a COVID-19 vaccine stacks up against some other common vaccines.<\/p>\n

\n
\n\n\n\n\n\n\n\n
Vaccine<\/strong><\/td>\nDisease<\/strong><\/td>\nHow well it works<\/strong><\/td>\n<\/tr>\n
Shingrix vaccine<\/td>\nShingles<\/td>\n97 percent overall efficacy in adults 50 and older; 90 percent efficacy for those 70 and older<\/td>\n<\/tr>\n
Seasonal flu vaccine<\/td>\nFlu<\/td>\nTypically 30\u201360 percent effective, depending on the year and how well it matches with circulating flu viruses<\/td>\n<\/tr>\n
Inactivated polio vaccine<\/td>\nPolio<\/td>\n90 percent effective or more with two doses; 99\u2013100 percent effective with three doses<\/td>\n<\/tr>\n
COVID-19 vaccine<\/td>\nCOVID-19<\/td>\nFDA recommends a minimum of 50 percent efficacy, could be higher<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<\/div>\n

 <\/p>\n

This story was originally published by\u00a0Science News<\/em><\/a>, a nonprofit independent news organization.<\/p>\n","protected":false},"excerpt":{"rendered":"

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