# Summary of the National Advisory Committee on Immunization (NACI) Statement—Recommendations on Fractional Influenza Vaccine Dosing in the Event of a Shortage: Pandemic preparedness

## TL;DR

This paper summarizes NACI's recommendations against using fractional influenza vaccine doses during shortages, based on limited evidence of effectiveness and feasibility issues.

## Contribution

The paper provides updated evidence-based guidance from NACI on fractional influenza vaccine dosing during pandemics.

## Key findings

- There was limited evidence for the effectiveness of fractional influenza vaccine dosing.
- Fair evidence was found for immunogenicity and safety, but feasibility issues were noted with intradermal use.
- NACI recommended against using fractional doses and instead prioritizing full doses for high-risk populations.

## Abstract

At the commencement of a pandemic, it is important to consider the impact of respiratory infections on the health system and the possibility of vaccine shortages due to increased demand. In the event of an influenza vaccine shortage, a strategy for administration of fractional influenza vaccine doses might be considered. This article reviews the available evidence for efficacy, effectiveness, immunogenicity and safety of fractional influenza vaccine dosing, and summarizes the National Advisory Committee on Immunization (NACI) recommendations on fractional dosing strategies by public health programs in Canada.

Two rapid literature reviews were undertaken to evaluate the efficacy, effectiveness, immunogenicity and safety of fractional influenza vaccine dosing via the intramuscular or intradermal route. The NACI evidence-based process was used to assess the quality of eligible studies, summarize and analyze the findings, and apply an ethics, equity, feasibility and acceptability lens to develop recommendations.

There was limited evidence for the effectiveness of fractional influenza vaccine dosing. Fractional dosing studies were primarily conducted in healthy individuals, mainly young children and infants, with no underlying chronic conditions. There was fair evidence for immunogenicity and safety. Feasibility issues were identified with intradermal use in particular.

NACI recommended that, in the event of a significant population-level shortage of influenza vaccine, a full-dose influenza vaccine should continue to be used, and existing vaccine supply should be prioritized for those considered to be at high risk or capable of transmitting to those at high risk of influenza-related complications or hospitalizations. NACI recommended against the use of fractional doses of influenza vaccine in any population.