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New research raises a question about whether receiving a fraction of a COVID-19 vaccine dose will still boost your immune protection while stretching the available vaccine supply for others.
Here's what it is and why it matters.

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What Is Dose-Stretching?

  • Definition: A method of distributing vaccines in smaller doses in an effort to spread the available vaccine supply to more people.
  • Has it been used before? Yes. In 2016, "dose-stretching" was used for millions of people in South America and Africa against an outbreak of yellow fever. At that time, the World Health Organization recommended cutting a typical vaccine dose to one-fifth. Researchers later found "the use of fractional-dose vaccination" was successful in "outbreak control" across age groups.

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New Study

  • Who / Where: Researchers at La Jolla Institute for Immunology's Center for Infectious Disease and Vaccine Research
  • What: Examined lower doses of Moderna's COVID-19 vaccine in a small group of 35 participants who received two doses of 25 micrograms - a combined half-dose of Moderna's typical dose per shot (100 mcg).
  • Results: After 7 months, researchers found that even with a lower dose, participants still had "durable" immunity to ward against COVID infections.

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"It is quite remarkable — and quite promising — that you can easily detect responses for that long a time."

Immunologist and co-author of the study, Asst. Prof. Daniela Weiskopf, Ph.D., on the results. Others not involved in the study also argue dose-stretching could lower infections, virus transmission, & deaths and slow the development of variants. However, concerns include possible public perception of lower vaccine doses as inferior - or if changing the dose could lead to more "vaccine resistance."

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"... some of these discussions about changing the dosing schedule or dose are based on a belief that changing the dose or dosing schedule can help get more vaccine to the public faster. However, making such changes that are not supported by adequate scientific evidence may ultimately be counterproductive to public health."

In January, the FDA addressed the possibility of dose-stretching, acknowledging that questions about lower doses are "reasonable" but "premature" due to lack of supporting data.

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Context: March 2020 was when the very first Americans received an experimental mRNA COVID-19 vaccine. One year later, the director of the CDC's National Center for Immunization and Respiratory Diseases said, "We have to stick with what we know works ..." Still, other researchers in a recent editorial (read it on our source page) argue developing nations don't have the time to wait and that dose-stretching should begin immediately. What do you think is the right call?

Jul 12, 2021

View All Quick Reads


    Nature Editorial: “Quarter-dose of Moderna COVID vaccine still rouses a big immune response”

    Nature Editorial: “Fractionation of COVID-19 vaccine doses could extend limited supplies and reduce mortality”

    • Click HERE to read the preprint study on lower doses of Moderna’s COVID-19 Vaccine
    • Click HERE for study: “Immunogenicity of Fractional-Dose Vaccine during a Yellow Fever Outbreak - Final Report”

    “CDC’s Messonnier: We can’t change the Covid-19 vaccine regimen unless we know it works” (STAT News, April 2021)

    Click HERE to read: “FDA Statement on Following the Authorized Dosing Schedules for COVID-19 Vaccines”

    March 2020: “NIH clinical trial of investigational vaccine for COVID-19 begins”