Model Predicts That 70% Vaccination Coverage Could Curb Pandemic

Abstract

Vaccination of 70% of the U.S. population could mitigate a severe epidemic of the pandemic influenza A(H1N1) virus, according to data from simulation models and analyses of existing studies. The research was published in the online edition of the journal Science.Researchers at the Fred Hutchinson Cancer Research Center in Seattle devised models for two scenarios: prevaccination of all age and risk groups before the pandemic influenza A(H1N1) virus becomes widespread in the United States, and phased vaccination (either universal or starting with children) over time as the epidemic progresses. Phased vaccination starts either at the beginning of the spread of disease or after a 30-day delay.All the vaccination strategies studied that involved a 70% coverage rate could have a significant mitigating effect on an H1N1 epidemic, the researchers said. “Clearly, combining vaccination with other mitigation measures, such as social distancing and targeted use of antiviral agents, could be quite effective,” wrote the team led by Yang Yang, PhD.The models in the study suggested that, with a 30-day delay after the spread of infection begins, a phased vaccination strategy starting with 70% of children aged 6 months to 18 years would mitigate an epidemic, as would a phased strategy that didn't prioritize children and didn't wait until 30 days into the spread of disease. But the models suggested that a universal strategy with a 30-day delay would be less effective, the researchers noted.Without knowledge of how well matched an H1N1 vaccine is to the virus, the researchers evaluated vaccination strategies involving both heterologous and homologous vaccines. A universal prevaccination protocol with a homologous vaccine and 70% vaccination coverage would significantly mitigate an epidemic. A 50% vaccine coverage rate would mitigate an epidemic spread to levels similar to that of a relatively mild seasonal flu epidemic. But a 30% rate of coverage would not be effective, the researchers stated.More research is needed to examine the logistics of vaccination with a limited vaccine supply, the researchers said. Vaccination of 70% of the U.S. population could mitigate a severe epidemic of the pandemic influenza A(H1N1) virus, according to data from simulation models and analyses of existing studies. The research was published in the online edition of the journal Science. Researchers at the Fred Hutchinson Cancer Research Center in Seattle devised models for two scenarios: prevaccination of all age and risk groups before the pandemic influenza A(H1N1) virus becomes widespread in the United States, and phased vaccination (either universal or starting with children) over time as the epidemic progresses. Phased vaccination starts either at the beginning of the spread of disease or after a 30-day delay. All the vaccination strategies studied that involved a 70% coverage rate could have a significant mitigating effect on an H1N1 epidemic, the researchers said. “Clearly, combining vaccination with other mitigation measures, such as social distancing and targeted use of antiviral agents, could be quite effective,” wrote the team led by Yang Yang, PhD. The models in the study suggested that, with a 30-day delay after the spread of infection begins, a phased vaccination strategy starting with 70% of children aged 6 months to 18 years would mitigate an epidemic, as would a phased strategy that didn't prioritize children and didn't wait until 30 days into the spread of disease. But the models suggested that a universal strategy with a 30-day delay would be less effective, the researchers noted. Without knowledge of how well matched an H1N1 vaccine is to the virus, the researchers evaluated vaccination strategies involving both heterologous and homologous vaccines. A universal prevaccination protocol with a homologous vaccine and 70% vaccination coverage would significantly mitigate an epidemic. A 50% vaccine coverage rate would mitigate an epidemic spread to levels similar to that of a relatively mild seasonal flu epidemic. But a 30% rate of coverage would not be effective, the researchers stated. More research is needed to examine the logistics of vaccination with a limited vaccine supply, the researchers said.