Seems to depend entirely what you read. I have read one computer magazine article recently that says android infections are significant and increasing. Another claims that apple does check its apps, but the google store identifies problem apps when they are reported to it. Some of the infections are on apps , some on drivebys when browsing so browsing may be the big issue even if safe apps only are used. Drivebys are turning up anywhere - often in adverts. If a driveby can install malware, or a downloader for it, and that will work on android, people will have a problem. If more and more people use undefended phones to browse, and are using those undefended connections for banking, in turn the hackers and malware makers are going to put more effort into breaking in.