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Evaluating the Prophylactic Efficacy of Baloxavir

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Dara Baker is a 2020–2021 Doximity Research Review Fellow. Nothing in this article is intended nor implied to constitute professional medical advice or endorsement. The views expressed in this article are those of the author and do not necessarily reflect the views/position of Doximity. 

With rising awareness about the spread of infectious disease, there has been a simultaneous acknowledgment of the limitations of prevention measures. Internationally, we are more aware than ever of the threat posed by respiratory droplets. For decades, public health officials have known that isolation, especially in known cases, mitigates the threat of infectious spread. However, prevention measures like physical distancing are difficult for many, particularly vulnerable populations in low-income communities for whom housing space is severely limited, or for adolescents living in dormitories. As such, medication may offer a means of limiting infectious spread in these, and in other, considerably “high-risk” situations. 

In a recent phase 3 clinical trial, baloxavir marboxil was compared to a placebo to test the efficacy of prophylaxis among the household contacts of patients with RT-PCR confirmed influenza virus. Baloxavir is approved in Japan and the U.S. for treatment of uncomplicated influenza A and B infection; yet, evidence of polymerase acidic protein (PA) mutation and viral resistance following its administration has curbed its use. The study results showed a significant decrease in influenza infections in the treatment group compared to the control. Additionally, those with lab-confirmed influenza in the baloxavir group exhibited a delayed onset of symptoms, with minimal adverse effects.

Overall, the design and execution of this trial were robust, and baloxavir demonstrated significant efficacy over placebo for prophylaxis of household contacts in a representative sample of individuals in Japan. These findings support the integration of baloxavir into clinical practice, perhaps offering a new tool for the mitigation of disease spread during influenza season — especially when distancing for many remains limited to the spacing of one small room.

In future research, it would be valuable to expand the use of baloxavir prophylaxis to members outside of the household, or to compare baloxavir to neuraminidase inhibitors in a non-inferiority study for prophylaxis. 

Dara Baker is a fourth-year medical student at GW SMHS, returning from her yearlong fellowship at NIH as part of the Medical Research Scholars Program, 2019–2020. She is an aspiring physician-scientist, excited about research in stem cell-based medicine, immunology, small molecule regulatory pathways, and genetics.

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