An Exploration on Heterologous/Homologous Boosters and COVID-19 Using the BEEHIVE Study Population

With Novavax's new 2023-2024 protein subunit vaccine, our primary objective was to compare the COVID-19 frequency of a specific heterologous booster combination (mRNA primer/Novavax protein booster) from a homologous mRNA one using the BEEHIVE study population. Our analysis included 973 participants (374 for Novavax, 368 for Pfizer, and 231 for the control). The COVID Rapid Antigen Test (RAT) results were then categorized by booster type: heterologous (mRNA primer/Novavax booster) or homologous (mRNA only). Each booster group was stratified by the number of vaccinations a participant received prior to joining the BEEHIVE study (2, 3, 4, or ‚â•5 doses). Odds ratios and chi-squared tests were calculated with a 95% confidence interval. Results showed that receiving a vaccination in general was associated with lower odds of testing positive for COVID-19: odds ratio was 0.549 (95% CI, [0.363, 0.838]). However, the analysis comparing heterologous vs homologous boosters found no significant difference in RAT COVID-19 positivity, except in the group receiving 3 mRNA doses prior to enrollment: odds ratio was 2.985 (95% CI, [1.190, 8.215]). Thus, the results of our analysis remain largely inconclusive as we were unable to reject the null hypothesis for the rest of the dosage groups. It is possible our study was too underpowered to detect a significant difference in this subgroup analysis. Additionally, hybrid immunity could be a potential confounder, as it was statistically associated with RAT COVID-19 positivity (p-value: 0.044), and further research investigating this relationship is needed.

An Exploration on Heterologous/Homologous Boosters and COVID-19 Using the BEEHIVE Study Population Authors: Soonyoung Kwon BA, Reese Hammer, Camil M. Rowan, Feiyun Yan MS, Josh Griffin MSHA, Jacob McKell BS, Hongwei Zhao ScD, Andrew L. Phillips MD, MOH, German L. Ellsworth MD, MPH, MOH, Matthew S. Thiese PhD, MSPH, Sarang K. Yoon DO, MOH Introduction Results • The COVID-19 vaccine has a diverse array of vaccine platforms, allowing for a wide range of primer/booster combinations to exist. • Studies have shown that certain heterologous boosters offer an immunological advantage over homologous boosters by increasing serum levels of IgG and CD8+ T cells, leading to a stronger immune response (Atmar et al., 2022; Orlandi et al., 2023). • Using the BEEHIVE study population, we aim to compare the frequency of COVID-19 between a homologous mRNA booster (Pfizer's 2023-2024 updated COVID-19 vaccine) and a heterologous protein subunit booster (Novavax’s 2023-2024 updated COVID-19 vaccine). • The odds ratios of a COVID-19 positive RAT for heterologous booster vs. un-boosted was 0.624 (95% CI, [0.389, 1.002]); homologous booster vs un-boosted was 0.474 (95% CI, [0.287, 0.781]). The odds ratio of the pooled boosted vs. the un-boosted group was 0.549 (95% CI, [0.363, 0.838]) (TABLE 1). • Directly comparing heterologous versus homologous boosters, odds ratios of a COVID-19 positive RAT and their 95% confidence intervals are shown in FIGURE 2, stratified by the number of vaccinations received before the BEEHIVE study. A statistically significant difference was found for the 3-dosage group only: 2.985 (95% CI, [1.190, 8.125]), which FIGURE 3 illustrates using bootstrap sampling distributions (n = 9999 samples). The 3-dosage group has a clear disparity in the frequency of COVID-19 positive RATs between the heterologous and homologous booster sampling distributions. TABLE 1: Contingency tables, split by booster type, listing the observed and expected counts of COVID positive and negative RATs for the boosted and control groups in the BEEHIVE study. The chi-squared test p-values, odds ratios and the OR Confidence Intervals are listed accordingly as well. The odds ratio at the bottom represents the pooled boosted vs the control group. *** indicates statistical significance. Methods • A total of 1176 participants enrolled in the BEEHIVE study and the surveillance period ran from November 2023 to August 2024. Those who opted for vaccination were randomized and given either the Novavax (n = 444) or Pfizer (n = 454) booster. 278 participants opted for no vaccination (un-boosted, nonrandomized comparator group). Each participant submitted weekly Rapid Antigen Self-Tests (RAT) for 24 weeks regardless of symptoms; positive results were confirmed through subsequent tests. • The BEEHIVE dataset was further processed, as detailed by the flow chart in FIGURE 1. Based on each participant’s BEEHIVE booster type, they were then labeled as heterologous (mRNA primer + Novavax booster, n = 375), homologous (mRNA primer + mRNA booster, n = 369) or control (un-boosted, n = 231) and compared. Within the vaccinated groups, participants were also stratified based on the number of vaccinations they received prior to study enrollment (2, 3, 4, or ≥5 doses). • The frequency of confirmed COVID-19 positive RATs was compared between the heterologous, homologous and control groups using chi-squared tests and odd ratios. All confidence intervals were set to 95%. Discussion • Despite the statistically significant findings for the three-dose group, the results of our analysis remain largely inconclusive as we were unable to reject the null hypothesis for the rest of the dosage groups. • This overall result may be expected as recent studies have observed that booster type shows little to no difference on COVID-19 prevalence at a population level (Asante et al., 2024). Additionally, hybrid immunity could be a potential confounder, as it was statistically associated with RAT COVID-19 positivity (chisquared test p-value: 0.044). • It is also possible our study was underpowered to detect a significant result in our subgroup analysis. Future studies investigating the impact of booster type for special patient populations, adverse events or hospitalizations rates are needed. FIGURE 2: A forest plot (log scale) showing the odds ratios and respective 95% Confidence Intervals for each dosage cohort, comparing the prevalence of COVID-19 between heterologous and homologous boosters. The actual values of the odds ratios are listed in TABLE 2, along with the lower and upper confidence levels. *** indicates statistical significance. FIGURE 3 Acknowledgements • Thank you to the University of Utah Health, Rocky Mountain Center for Occupational and Environmental Health (RMCOEH), and the Division of Occupational and Environmental Health. • This study was funded and supported by Novavax. References FIGURE 1: A flow chart displaying our logic and thought process when further filtering the BEEHIVE dataset. All exclusionary criteria were justified based on previous COVID-19 research, or due to incomplete/inconclusive results. Ultimately, 975 of the 1176 participants were kept (744 boosted/231 control). 4/1/2025 FIGURE 3: Histograms and distribution plots showing the proportions of COVID positive cases within bootstrapped samples for heterologous and homologous boosters (n = 9999 samples). The graph on the left represents the three-dose cohort (3 vaccinations received before BEEHIVE) while the graph on the right represents the four-dose cohort (4 vaccinations received before BEEHIVE). • Asante, M. A., Michelsen, M. E., Balakumar, M. M., Kumburegama, B., Sharifan, A., Thomsen, A. R., Korang, S. K., Gluud, C., & Menon, S. (2024). Heterologous versus homologous COVID-19 booster vaccinations for adults: Systematic review with meta-analysis and trial sequential analysis of randomised clinical trials. BMC Medicine, 22(1), 263. https://doi.org/10.1186/s12916-024-03471-3 • Atmar, R. L., Lyke, K. E., Deming, M. E., Jackson, L. A., Branche, A. R., El Sahly, H. M., Rostad, C. A., Martin, J. M., Johnston, C., Rupp, R. E., Mulligan, M. J., Brady, R. C., Frenck, R. W., Bäcker, M., Kottkamp, A. C., Babu, T. M., Rajakumar, K., Edupuganti, S., Dobrzynski, D., … Beigel, J. H. (2022). Homologous and Heterologous Covid-19 Booster Vaccinations. New England Journal of Medicine, 386(11), 1046–1057. https://doi.org/10.1056/NEJMoa2116414 • Orlandi, C., Stefanetti, G., Barocci, S., Buffi, G., Diotallevi, A., Rocchi, E., Ceccarelli, M., Peluso, S., Vandini, D., Carlotti, E., Magnani, M., Galluzzi, L., & Casabianca, A. (2023). Comparing Heterologous and Homologous COVID-19 Vaccination: A Longitudinal Study of Antibody Decay. Viruses, 15(5), 1162. https://doi.org/10.3390/v15051162 1