Not so long ago, vaccines were a distant light at the end of the quarantine tunnel. Now, vaccination is beginning to reach a broad spectrum of the American public, and it is expanding globally. As vaccines have come out, there has been considerable controversy about who should be prioritized for vaccination. Healthcare and essential workers have potentially the greatest exposure while the oldest age groups experience the greatest mortality and younger age groups have greater transmission rates.
A new study from the University of Waterloo has developed an advanced model to address this very question. They integrated epidemiological data using a susceptible-exposed-presymptomatic-asymptomatic-symptomatic-removed model with models of quarantine and prevention measure compliance based on numerous social and epidemiological factors to develop a more thorough model. Using this model, they compared the effectiveness of four vaccination strategies: oldest first, youngest first, uniform (everyone has the same priority), and contact-based (giving to people with the highest transmission rates first such as younger groups). They found that, while vaccinating oldest first was the most effective at preventing deaths in some cases, the contact-based and uniform methods sometimes had higher effectiveness – especially when a larger proportion of the population had already had the disease. They also found that the youngest first strategy generally performed worse than the other techniques since young populations tend to transmit to other young individuals which results in an uneven distribution of protection.
Overall, this study indicates that vaccine distribution programs may need to rethink to whom they vaccinate first; however, the authors note that there are still significant factors not included in their model including effects of racial & gender demographics and different transmission dynamics in settings such as nursing homes and hospitals.