I want to begin my remarks by highlighting an exciting milestone, we took past 15% of our patients dialyzing at home.
This means that approximately 30,000 of our patients receive the clinical and lifestyle benefits of home dialysis.
Our current network of centers provides that easy access such that 80% of our dialysis patients live within 10 miles of a DaVita home center.
On to our Q3 results.
Q3 operating income grew approximately 9% year-over-year, and adjusted earnings per share grew by more than 31% over the same period However, the ongoing COVID pandemic continues to take its toll on too many human lives in the world at large, and among our patients.
Incremental mortality increased from fewer than 500 in Q2 to approximately 2000 in Q3.
After quarter end, COVID infections continue to decline, with our new case count during the week ending October 16 down by approximately 60%, relative to the recent Delta peak.
Switching to vaccines, approximately 73% of our patients have now been vaccinated.
At the end of Q3, we now have over 22,000 patients in some form of integrated care arrangements, representing 1.7 billion of value-based care contracts.
Operating income was $475 million and earnings per share was $2.36.
Our Q3 results include a net COVID headwind of approximately $55 million, an increase relative to the quarterly impact that we experienced in the first half of the year.
As Javier mentioned, the latest COVID surge resulted in excess mortality in the quarter of approximately 2000 compared to fewer than 500 in Q2.
Our current view of the OI impact of COVID for the year is worse by approximately $40 million compared to our expectations from last quarter.
For 2021, we now expect a total net COVID impact of approximately $210 million.
Treatments per day were down by 536 or 0.6% in Q3 compared to q2.
In addition, the quarter had a higher ratio of Tuesdays, Thursdays and Saturdays, which lowered treatments per day for the quarter by approximately 300.
Revenue per treatment was essentially flat quarter-over-quarter, patient care cost per treatment was up approximately $5 quarter-over-quarter, primarily due to higher teammate compensation and benefit expenses.
Other loss for the quarter was 7.6 million, primarily due to a $9 million decline in the mark to market of our investment in Miromatrix.
The value of this investment at quarter end was $14 million.
Now that we've seen the impact of the Delta surge, we are increasing our estimate of COVID impact for the year by $40 million.
Given where we are in the year, we are now incorporating this COVID impact into our revised adjusted OI guidance of $1.76 billion to $1.81 billion.
We are also narrowing our guidance for adjusted earnings per share to $8.80 to $9.15 per share.
And we are maintaining our free cash flow guidance of $1 billion to $1.2 billion, although there is some chance that our free cash flow may fall below the bottom end of the range, depending on the timing of our DSO recovery.
Our guidance anticipates Q4 operating income to be negatively impacted by approximately $75 million of seasonally high or one-time items, including certain compensation expenses, elevated training costs, higher health benefit expenses, and G&A.
We anticipate a year-over-year incremental investment in the range of $15 million as we continue to grow our ITC business.
And we will also begin depreciating our new clinical IP platform, which we expect to be approximately $40 million.
We are anticipating the end of the temporary sequestration suspension, which would be a $70 million headwind for the full year.
Our current estimate is a net headwind of $50 million to $75 million.
While the range of potential outcomes for 2022 is broad, a reasonable scenario could result in an OI decline of $150 million from our 2021 guidance.
Finally, during the third quarter, we repurchase 2.7 million shares of our stock and in October to date, we repurchased an additional 1.2 million shares.

Summary:
On to our Q3 results.
Operating income was $475 million and earnings per share was $2.36.
We are also narrowing our guidance for adjusted earnings per share to $8.80 to $9.15 per share.