In a previous post about R01s, I noted that the fraction of the NIH budget going to R01s decreased over the period from FY2003 to FY2013. This fact is of concern, of course, for a variety of reasons. But first, it is important to understand the observation as completely as we can. One set of factors that has contributed is the growth in the number of R21 awards, driven in large part by a huge increase in the number of R21 applications and the introduction of additional mechanisms.
For the R21 mechanism, the numbers of applications and awards NIH-wide for the period from FY2003 to FY2013 are shown below:
These data reveal that the number of applications increased more than 2.6-fold from 5283 in FY2003 to almost 14000 in FY2012. NIH responded to this "proposal pressure" by increasing the number of awards from 1255 in FY2003 to almost 2000 in FY2012. Nonetheless, the success rate for R21s has remained between 12.9 and 14.9 % over the past five years, generally 2 or more percentile points below the R01 success rate, even for new (as opposed to competing renewal) applications. Thus, the competition for R21 awards is more severe that it is for R01 awards, a fact which is not, in my experience, widely appreciated by the all in the community.
When I was Director of NIGMS, we decided to stop accepting unsolicited R21 applications. This decision was made for two reasons. First, we found the peer review process for R21s quite frustrating. NIGMS was trying to use the R21 mechanism to support "high risk-high potential reward" research, that is, new ideas for which a modest investment could provide a proof of principle that could be used to drive future inquiry. However, despite efforts by CSR and NIGMS staff to orient reviewers, we frequently received scores and summary statements that did not align e.g. 'This is a potentially important and impactful project, but there is no preliminary data' and a bad score or 'This is a solid proposal supported by much preliminary data' with a good score. Because of this, we often struggled to develop sensible paylists. NIH made this problem worse by using the R21 mechanism for many other purposes other than the "high risk-high potential reward" goal. This confused reviewers, applicants, and even NIH staff.
Second, we had misgivings about whether the duration of the R21 and the size of the award would, in general, support substantial research compared to taking the same funds and supporting a smaller number of R01-sized grants. This led to the EUREKA R01 awards, used by NIGMS and a few other institutes.
I do not know of any studies that bear of the success of R21 awards in promoting scientific discovery or in keeping investigators "in the game". One interesting observation is that, in FY2013, more than 2300 (62%) of the R21 awards were held by investigators who had no other R21 or R01 awards (competing or non-competing) in the same year. Looking back to earlier year, one could track subsequent results for such investigators if that would be of interest.