Half-dose COVID-19 boosters have fewer side effects and cost-effective

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Researchers from the Murdoch Children’s Research Institute (MCRI) and the National Center for Communicable Diseases in Mongolia conducted a study to assess the efficacy of using a half-dose Pfizer COVID-19 booster vaccine.

This research is part of a larger international clinical trial, including countries like Australia and Indonesia, aiming to optimize COVID-19 vaccination strategies.

The first set of results from this study, published in The Lancet Regional Health—Western Pacific, involved 601 Mongolian adults.

The study revealed that a half dose of the Pfizer booster, following primary vaccination with either AstraZeneca or Sinopharm, elicited a strong immune response comparable to a full dose, with the added benefits of fewer side effects and reduced costs.

However, it indicated that this fractional dosing might be less effective for those who initially received the Sputnik V vaccine.

Advantages of Half-Dose Boosters

The study highlights several advantages of using a half-dose Pfizer booster:

Similar Immune Response: The half-dose booster generated an immune response that was non-inferior to the full dose.

Fewer Side Effects: Participants who received the half-dose reported significantly fewer local and systemic reactions, such as pain, fever, vomiting, diarrhea, and headaches.

Cost-Effectiveness: Reducing the dosage can make the vaccination process more economical, potentially allowing broader access, especially in low- and middle-income countries.

Implications for Global Vaccination Strategies

This research offers valuable insights for policymakers and immunization advisory committees, suggesting that flexible dosing schedules could be an effective approach to boost vaccination uptake and manage costs in COVID-19 booster programs.

The idea of fractional dosing is particularly appealing for enhancing vaccine accessibility in resource-limited settings.

Ongoing Research and Future Directions

Participants in the study will be monitored for up to 12 months, providing further data on the durability of the immune response, the rate of waning immunity, and the incidence of breakthrough infections.

This ongoing research is crucial for refining booster strategies and ensuring effective long-term protection against COVID-19.


The findings from the MCRI-led study offer a promising alternative to standard full-dose boosters.

The possibility of using half-dose Pfizer boosters could play a significant role in global efforts to combat COVID-19, especially in terms of improving vaccine accessibility and reducing healthcare costs while maintaining a robust immune response.

If you care about COVID, please read studies about new evidence on rare blood clots after COVID-19 vaccination, and how diets could help manage post-COVID syndrome.

For more information about health, please see recent studies about COVID-19 infection and vaccination linked to heart disease, and results showing extracts from two wild plants can inhibit the COVID-19 virus.

The research findings can be found in The Lancet Regional Health—Western Pacific.

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