However, the research on IFAP and asthma exacerbations in the United States has relied on small sample sizes and/or self-reported outcomes [5,7,8,9,10], and studies that have used clinically-documented events, from the Netherlands, reported no association or a protective association of IFAP and asthma exacerbations [14,15,16]. Here, MBTPS2 is linked to asthma.