A yearly flu vaccine is crucial for protecting yourself from the flu, according to the Centers for Disease Control and Prevention (CDC). However, because of limited vaccine supply, the demand in some regions cannot always be met, especially during a pandemic.

Health experts determine the ideal vaccine formula each season, which is then produced in small batches, leading to uneven supply and demand while vaccine production ramps up. Historically, due to fairness considerations, vaccines have been allocated pro rata, which means proportionally based on the population of a region. While this may seem like the best way to fairly distribute a limited supply, it does not take demand and “uptake” — the number of people who are willing to be vaccinated — into account.

“The uptake rate can vary by region, for various reasons.” explained Pinar Keskinocak, William W. George Chair and professor in the H. Milton Stewart School of Industrial and Systems Engineering, College of Engineering ADVANCE Professor, and co-founder and director of the Center for Health and Humanitarian Systems (CHHS). “If the limited vaccine inventory is allocated proportionally to the population in different regions without considering the uptake rate, unused vaccine inventory may pile up in some areas while other areas experience shortages.”

With the goal of better matching supply and demand, Zihao Li (Ph.D. 16), Keskinocak, and CHHS co-founder and Professor Julie Swann (BIE 1996) from NC State University proposed a new allocation strategy, where the limited vaccine inventory is allocated pro rata only to those regions that continue to experience a positive uptake rate. They developed a simulation model to compare the current and proposed vaccine allocation strategies.

“We found that the proposed strategy would benefit the entire population because it leads to a higher number of people vaccinated and less inventory leftover,” explained Keskinocak.

However, vaccine inventory visibility in public health supply chains is limited, and accurate uptake rates may not always be available in each geographic area. Keskinocak hopes the results of the study will encourage local reporting of both the number of vaccines administered during a season and the amount that is unused, to inform future allocation decisions.

Optimizing the flu vaccine supply chain will also help when the next pandemic strikes. Historically, pandemics occur every 30-40 years, but the results can be devastating. According to the CDC, the 2009 H1N1 influenza pandemic resulted in 60.8 million illnesses and 12,469 deaths in the U.S. alone.

“Information about uptake rates is even more important during a pandemic,” added Keskinocak, “not only for the effective allocation of vaccines to slow the spread of the disease, but also to increase public awareness efforts about vaccinations in areas where uptake is low.”

This study was supported by a seed grant from Georgia Tech and Children’s Healthcare of Atlanta. This research was also supported in part by the Harold R. and Mary Anne Nash Junior Faculty Endowment Fund and the following Georgia Tech benefactors: William W. George, Andrea Laliberte, Joseph C. Mello, and Richard “Rick” E. and Charlene Zalesky.