[Price effects of global vaccine pooled procurement]

To evaluate the impact of international pooled procurement mechanisms, which are primarily represented by the United Nations Children ' s Fund (UNICEF) and the Pan American Health Organization (PAHO), on the procurement prices of vaccines.

Based on 14 497 vaccine procurement transaction records collected from 188 different countries spanning the period from 2013 to 2024, this research employed a high-dimensional fixed effects model along with an event study metho-dology to accurately identify the price effects and dynamic temporal trends, while simultaneously conducting a multidimensional heterogeneity analysis.

(1) The baseline model demonstrated that, when compared to the independent self-procurement conducted by individual nations, utilizing pooled procurement through the UNICEF significantly reduced the average vaccine prices by 27.6% (β=-0.323, P < 0.01). The PAHO mechanism similarly exhibited an initial price reduction potential of approximately 30.9% (β=-0.370, P=0.052). (2) The event study method strictly validated the parallel trend assumption (joint significance test of pre-treatment coefficients: F=0.27, P=0.845). Dynamic tracking revealed that a price reduction of approximately 30.0% (β=-0.356, P < 0.01) was achieved exactly in the year of transitioning from self-procurement to pooled procurement, and this reduction effect remained persistently stable in subsequent years. (3) Heterogeneity tests revealed a significant "pro-poor" effect of pooled procurement: the price reduction margin obtained by small-scale buyers (38.5%, β=-0.487, P < 0.01) was significantly higher than that of large-scale buyers (22.5%, β=-0.255, P < 0.01). The marginal price reduction coefficient for non-Global Alliance for Vaccines and Immunization (GAVI) eligible countries (β=-0.418, P < 0.01) was substantially larger than that for GAVI eligible countries (β=-0.118, P < 0.05). The high-income country group experienced the most substantial price drop (β=-0.475, P < 0.01). (4) The supply-side moderating effect analysis indicated that UNICEF' s collective bargaining power maintained robustness across diverse market structures, showing no statistically significant attenuation despite increases in market concentration (interaction term β=0.095, P>0.10).

Institutionalized pooled procurement mechanisms are capable of significantly reducing vaccine prices. For those countries that are currently in the immunization financing transition period, as well as those facing high self-procurement benchmark prices, participating in an efficient international pooled procurement platform serves as a critical institutional arrangement to replace external financial aid and to effectively maintain the long-term affordability of vaccines.