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Trial of 2nd Booster Dose of COVID-19 Vaccine

NCT05539703 · Status: WITHDRAWN · Phase: NA · Type: INTERVENTIONAL

Last updated 2025-05-29

No results posted yet for this study

Summary

Background Recent studies indicate that a 2nd booster dose is associated with lower risk of severe COVID-19. The studies are based on Israeli registry data, comparing outcomes among individuals who have taken the booster, or not. Interpreting the findings from such non-experimental studies is challenging - there are likely systematic differences between those who accept the offer to take a booster dose, and those who do not.

Aim Determine the effect of offering vaccination with a 2nd COVID-19 booster dose on severe COVID-19, measured by hospitalization and death caused by COVID-19.

Methods Intervention group: A random sample drawn from the whole population aged 45-64 years with 3 doses of COVID-19 vaccine will receive a personal offer to receive the 4th dose of a COVID-19 vaccine in their municipality.

Control group: The rest of the population aged 45-64 with 3 doses, who will receive no such offer.

Randomization: The investigators will draw a set of birth dates - can then see who is in the intervention group in Beredt C19 (Norwegian emergency preparedness register for COVID-19) without identifying them individually (personal identification numbers are encrypted).

Primary outcome: Hospitalization or death caused by COVID-19 in a period of 10 weeks after invitations are sent.

Sample size calculations: 300 000 individuals in the intervention group, assuming risk of the primary outcome is at least 15% lower in the intervention group. (The investigators expect a large proportion NOT to accept the invitation to take the vaccine).

Conditions

Interventions

OTHER

Invitation to get a 2nd booster dose of COVID-19 vaccine

Participants in the intervention group will receive an invitation to get a 2nd COVID-19 booster dose. Those who accept the invitation to be vaccinated will receive the vaccine through their municipality's vaccination service.

Sponsors & Collaborators

  • Norwegian Institute of Public Health

    lead OTHER_GOV

Principal Investigators

  • Atle Fretheim, PhD MD · Norwegian Institute of Public Health

Study Design

Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
SINGLE
Model
PARALLEL

Eligibility

Min Age
45 Years
Max Age
64 Years
Sex
ALL
Healthy Volunteers
Yes

Timeline & Regulatory

Start
2022-10-31
Primary Completion
2023-01-31
Completion
2023-06-30

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Diseases

Read the full study record

This page highlights key information. For complete eligibility criteria, study locations, investigator contacts, and the full protocol, visit the original record on ClinicalTrials.gov.

View NCT05539703 on ClinicalTrials.gov