Optimizing future COVID-19 vaccine allocation can double efficacy

In anticipation of the introduction of the coronavirus disease (COVID-19) vaccine, researchers in Australia and the United States used a mathematical model of age structure to allocate age-specific doses to control SARS-CoV-2 infection. We evaluated the potential benefits of optimizing. Vaccination alone may not be sufficient to achieve herd immunity in some situations. Research is currently medRxiv* Preprint server.

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is notorious for being highly infectious and cumbersome to contain, so a safe and sufficiently effective vaccine is needed to completely control the pandemic. is.

However, the introduction of the first vaccine should be targeted not only to those who are at greatest risk of developing an infection or disease, but also to those who are most responsible for an ongoing infection. In other words, targeting age groups that further contribute to the transmission of infection can dramatically increase the effectiveness of COVID-19 vaccination.

Current estimates of the SARS-CoV-2 herd immunity threshold are 60-70%. This corresponds to about 90% of the total population vaccination rate, if there is a vaccine that is at least 70% effective. However, incorporating population heterogeneity can result in significantly lower thresholds.

This is due to the young to middle-aged group with high contact rates, infectivity and susceptibility to infection. Eliminating these individuals from the sensitive pool will, in turn, have a disproportionate impact on communication potential.

Such observations suggest that age-specific characteristics of both social mix and SARS-CoV-2 infection may be used to increase the efficiency of future vaccine campaigns. It is the center of the strategy.

This is a research group led by Dr. Michael T. Meehan of the Australian Institute of Tropical Health Medicine. James Cook University In Townsville, Australia, we recently developed a mathematical model that optimizes age-specific dose distribution and provides a global distribution of the minimum vaccination rates required to achieve herd immunity. Dr. Meehan Australian National University, Monash University And that University of Hawaii at Manoa..

Modeling of vaccination rate levels

To estimate the age-specific infection rate of infected individuals in 179 countries, this study assimilated age-dependent susceptibility and disease severity tailored to COVID-19 patient data, age group SARS-CoV- 2 Infection models have been adopted.

Researchers then used a candidate vaccine profile developed by the World Health Organization to select optimized targets designed to reduce transmission, defined through a reduction in effective reproduction numbers or R. .._eff.. Investigating alternatives in this range also explained the parameter uncertainty.

Two separate mechanisms of action for vaccine candidates were investigated: one that reduces the recipient’s susceptibility to infection and one that prevents the development of symptomatic disease in individuals infected with SARS-CoV-2.

In addition, the cost and feasibility of deploying age-specific vaccines was not considered to avoid over-guessing. Nonetheless, in addition to the optimal global solution identified for each age group / setting, researchers can choose about the same (within 1%) transmission if it proves to be more costly. We also specified a range of possible age-specific coverage levels with potential reductions-effective.

Customized age-specific vaccination strategies

In 179 countries included in this study, researchers found that the highest-priority individuals belonged to individuals aged 30-59 years, primarily due to high contact rates and high risk of infection and illness. ..

“Whether the goal is to minimize infection at a certain dose, or to minimize the dose required to achieve a certain reduction in infection, our analysis states: It shows that dose requirements or infection rates can be halved under a coordinated age-based vaccination strategy, further explaining the study’s authors.

In any case, this paper shows that it is less than 100% vaccine. Effectiveness Although significant population-level coverage may be required to achieve herd immunity, this threshold is the target vaccine, as suggested by specific studies that explain population susceptibility and mixed heterogeneity. It can be significantly reduced by inoculation.

Age distribution and infection rate by age. Population pyramid (panel AC) and transmission matrix (panel DF) of India (left), China (center), United Kingdom (right). In panel DF, the colors in the i-th row and j-th column of the transmission matrix represent the average number of infections in age group i generated by individuals in age group j during the course of the COVID-19 infection episode. The elements of each matrix are rescaled so that the maximum eigenvalues ​​of each transmission matrix match the basic reproduction number (R0) estimated by Abbott et al.15, or India. China: 2.6; and United Kingdom: 2.3.

Practical meaning

If you find a globally available approved COVID-19 vaccine, the initial supply is definitely limited, so an important step is to allocate the dose in the most efficient way to reduce viral infection. ..

“Our study found that vaccination allocation settings and age-specific optimizations were significantly more efficient than uniform vaccination programs, saving up to half of the available doses, and in some settings. It shows that the same reduction in transmission can be achieved, “the study author emphasizes.this medRxiv paper.

In addition, this analysis highlights the often overlooked and unattractive result that vaccination alone may not be sufficient to completely suppress COVID-19.

The authors then state that this could open the door to permanent control measures alongside vaccination protocols. This may include improved social distance and hygiene. But for now, you can wait for the first vaccine on the market to work in a real environment.

Global target immunization coverage under a unified vaccination policy. Map of the minimum target vaccination range required to achieve herd immunity under a uniform vaccine allocation program. Countries colored bright yellow cannot achieve herd immunity by vaccination alone (that is, the minimum coverage threshold is above 100%).

*Important Notices

medRxiv Publish preliminary scientific reports that should not be considered definitive as they are not peer-reviewed, guide clinical practice / health-related behaviors, and should not be treated as established information.