The letter by Gwynneth Kelley on March 22 regarding the effectiveness of masks (“What if masks only protect us by 2 percent?”) completely distorts the CDC study it references.
It is easy to be confused by the study’s conclusions. The study says that the implementation of mask mandates reduced the growth rates of COVID-19 cases by 1.1, 1.5, 1.7, and 1.8 percentage points within 21-40, 41-60, 61-80 and 81-100 days, respectively, after implementation.
Gwynneth Kelley correctly quotes the report, but then, in the next paragraph, claims that these percentages are reductions in the chances of getting COVID-19, not reductions in growth rates.
A small reduction in growth rates leads to huge reductions in cases over time. So, if cases are growing at 5 percent per day and that growth rate dropped to 3.5 percent, the total number of cases would expand by less, substantially, over time. It’s like your mortgage. A small drop in your mortgage rate leads to huge savings over time.
The study concludes that mask mandates (as well as restaurant closures which were also studied in the report) are effective and important tools in reducing the spread of COVID-19.
Wear a mask!