Fractional dose vaccination is a strategy to reduce the dose of a

vaccine A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified. ...

to achieve a vaccination policy goal that is more difficult to achieve with conventional vaccination approaches, including deploying a vaccine faster in a

pandemic A pandemic () is an epidemic of an infectious disease that has spread across a large region, for instance multiple continents or worldwide, affecting a substantial number of individuals. A widespread endemic disease with a stable number of i ...

, reaching more individuals in the setting of limited healthcare budgets, or minimizing side effects due to the vaccine. Fractional dose vaccination exploits the nonlinear dose-response characteristics of a vaccine: If two persons can be vaccinated instead of one, but each one gets 2/3 of the protective efficacy, there is a net benefit at society scale for reducing the number of infections. If the healthcare budget is limited or only a limited amount of vaccine is available during the early phase of a pandemic, this can make a difference for the total number of infections. Fractional dose vaccination uses a fraction of the standard dose of a regular vaccine that is administered by the same, or an alternative route (often

subcutaneously The subcutaneous tissue (), also called the hypodermis, hypoderm (), subcutis, superficial fascia, is the lowermost layer of the integumentary system in vertebrates. The types of cells found in the layer are fibroblasts, adipose cells, and ma ...

or intradermally). Fractional dose vaccination has been used or proposed in a number of relevant infectious poverty diseases including

yellow fever Yellow fever is a viral disease of typically short duration. In most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains – particularly in the back – and headaches. Symptoms typically improve within five days. In ...

poliomyelitis Poliomyelitis, commonly shortened to polio, is an infectious disease caused by the poliovirus. Approximately 70% of cases are asymptomatic; mild symptoms which can occur include sore throat and fever; in a proportion of cases more severe sym ...

COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was identified in Wuhan, China, in December 2019. The disease quickl ...

Use

In the context of limited healthcare budgets

During the 2016 yellow fever outbreak in Angola and the Democratic Republic of the Congo, the WHO approved the use of fractional dose vaccination to deal with a potential shortage of vaccine. In August 2016, a large vaccination campaign in Kinshasa used 1/5 of the standard vaccine dose. In 2018 it was reported that fractional dose vaccination with 1/5 of the standard vaccine dose, administered intradermally, conferred protection for 10 years, as documented by a randomized clinical trial. In

Polio Poliomyelitis, commonly shortened to polio, is an infectious disease caused by the poliovirus. Approximately 70% of cases are asymptomatic; mild symptoms which can occur include sore throat and fever; in a proportion of cases more severe sym ...

myelitis, fractional dose vaccination has been shown to be effective while reducing overall cost, rendering polio vaccination available to more individuals.

In the Covid-19 pandemic

In a pandemic wave, fractional dose vaccination is considered to accelerate widespread access to vaccination when vaccine supply is limited: In the

COVID-19 pandemic The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identified ...

, epidemiologic models predict a major benefit of personalized fractional dose vaccination strategies with certain vaccines in terms of case load, deaths, and shortening of the pandemic.

To reduce side effects

In some segments of the population, disease risk is lower but specific vaccine side effect risks may be increased. In such subpopulations, fractional dose vaccination might optimize the benefit-risk ratio of vaccination for an individuum and optimize the cost-benefit relation for society.

References

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