Trial reportVaccine2022
A randomized clinical trial of a booster dose with low versus standard dose of AZD1222 in adult after 2 doses of inactivated vaccines.
Trial report in Vaccine, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 12 papers.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
12 citing papers in PubMed.
- Fractional BNT162b2 boosters induce durable immune responses after non-mRNA priming in Mongolia: a randomised controlled trial.Frontiers in immunology · 2026Trial
- Immunogenicity, safety and reactogenicity of heterologous (third dose) booster vaccination with a full or fractional dose of two different COVID-19 vaccines: A phase 4, single-blind, randomized controlled trial in adults.Human vaccines & immunotherapeutics · 2023Trial
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- Immunogenicity and reactogenicity of fractional vs. full booster doses of COVID-19 vaccines: a non-inferiority, randomised, double-blind, phase IV clinical trial in Brazil.Lancet regional health. Americas · 2025Article
- Antispike IgG antibody decay after immunisation with fractional versus full booster doses of COVID-19 vaccines: a 6-month longitudinal analysis of the FRACT-COV trial in Brazil.BMJ public health · 2025Article
- Article
- Immunogenicity of BNT162b2 in children 6 months to under 5 years of age with previous SARS-CoV-2 infection, in the era of Omicron predominance.Vaccine: X · 2023Article
- Long-term immunogenicity in previously vaccinated healthcare workers with inactivated virus vaccine after SARS-CoV-2 infection or booster vaccination.Vaccine: X · 2023Article
- Cost effectiveness of fractional doses of COVID-19 vaccine boosters in India.Med (New York, N.Y.) · 2023Article
- Heterologous Prime-boost of SARS-CoV-2 inactivated vaccine and mRNA BNT162b2 among Healthy Thai Adolescents.Vaccine: X · 2022Article
- Article
- Article
Corrections and comments
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Authors and funding
13 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
backgroundImmunogenicity of inactivated SARS-CoV-2 vaccine has waning antibody over time. With the emergence of the SARS-CoV-2 delta variant, which requires higher neutralizing antibody to prevent infection, a booster dose is needed.
objectiveTo evaluate immunogenicity and reactogenicity of standard- versus low-dose ChAdOx1 nCoV-19 vaccine booster after CoronaVac in healthy adults.
methodsA double-blinded, randomized, controlled trial of adult, aged 18-59 years, with completion of 2-dose CoronaVac at 21-28 days apart for more than 2 months was conducted. Participants were randomized to receive AZD1222 (Oxford/AstraZeneca) intramuscularly; standard dose (SD, 5x10
resultsFrom July-August 2021, 422 adults with median age of 44 (IQR 36-51) years were enrolled. The median interval from CoronaVac to AZD1222 booster was 77 (IQR 64-95) days. At baseline, geometric means (GMs) of sVNT against delta variant and anti-S-RBD IgG were 18.1%inhibition (95% CI 16.4-20.0) and 111.5 (105.1-118.3) BAU/ml. GMs of sVNT against delta variant and anti-S-RBD IgG in SD were 95.6%inhibition (95% CI 94.3-97.0) and 1975.1 (1841.7-2118.2) BAU/ml at day 14, and 89.4%inhibition (86.4-92.4) and 938.6 (859.9-1024.4) BAU/ml at day 90, respectively. GMRs of sVNT against delta variant and anti-S-RBD IgG in LD compared to SD were 1.00 (95% CI 0.98-1.02) and 0.84 (0.76-0.93) at day 14, and 0.98 (0.94-1.03) and 0.89 (0.79-1.00) at day 90, respectively. LD recipients had significantly lower rate of fever (6.8% vs 25.0%) and myalgia (51.9% vs 70.7%) compared to SD.
conclusionHalf-dose AZD1222 booster after 2-dose inactivated SARS-CoV-2 vaccination had non-inferior immunogenicity, yet lower systemic reactogenicity. Fractional low-dose AZD1222 booster should be considered especially in resource-constrained settings.
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