Cost of revenues
We had cost of revenues of $1.0 million for each of the three months ended June 30, 2022 and 2021. As a percentage of revenues, cost of revenues decreased to 6% in the second quarter of 2022 as compared to 7% in the prior year period.
Engineering and product development expense
We had engineering and product development expense of $1.1 million for the three months ended June 30, 2022, an increase of $0.1 million, or 13%, compared to $1.0 million in the same period of the prior year. The increase was primarily due to increased headcount and annual pay increases in line with our business expansion, increases in dues and subscriptions and consulting costs associated with ongoing projects to extend QuantaFlo to additional cardiovascular diseases. As a percentage of revenues, engineering and product development expense was at 7% in the second quarter of each of 2022 and 2021.
Sales and marketing expense
We had sales and marketing expense of $4.2 million for the three months ended June 30, 2022, an increase of $0.6 million, or 16%, compared to $3.6 million in the same period of the prior year. The increase was primarily due to increased headcount and annual salary increases, and associated expense to serve a continued expansion of customer activities. As a percentage of revenues, sales and marketing expense increased to 28% in the second quarter of 2022, as compared to 25% in the prior year period.
General and administrative expense
We had general and administrative expense of $3.4 million for the three months ended June 30, 2022, an increase of $1.1 million, or 50%, compared to $2.3 million in the same period of the prior year. The increase was primarily due to the growth in our business, which led to increased expenses including insurance, compensation due to increased headcount and annual salary increases, information technology related subscriptions, legal, and other professional fees. As a percentage of revenues, general and administrative expense increased to 23% in the second quarter of 2022, as compared to 16% in the prior year period.
Other income
We had total other income of $14.0 thousand for the three months ended June 30, 2022 compared to $9.0 thousand in 2021. The increase of $5.0 thousand from the prior year period is primarily due to a $4.0 thousand increase in interest income and a gain on sale of old equipment of $1.0 thousand, which was partially offset by credit card merchant fees.
Income tax provision (benefit)
We had income tax provision of $1.1 million for the three months ended June 30, 2022, an increase of $1.3 million or 619%, compared to income tax benefit of $0.2 million in the same period of the prior year. The change was primarily due to lower tax benefits associated with stock-based compensation plans.
Net income
We had net income of $4.1 million, or $0.60 per basic share and $0.51 per diluted share, for the three months ended June 30, 2022, a decrease of $2.6 million, or 39%, compared to a net income of $6.7 million, or $1.00 per basic share and $0.83 per diluted share, for the same period of the prior year.
Six Months Ended June 30, 2022 Compared to Six Months Ended June 30, 2021
Revenues
We had revenues of $28.8 million for the six months ended June 30, 2022, an increase of $1.3 million, or 5%, compared to $27.5 million in the same period in 2021. Our revenues are primarily from fees charged to customers for use of our vascular testing products and from sales of accessories used with these products. We recognized revenues of $28.3 million from fees for our vascular testing products for the six months ended June 30, 2022, consisting of $16.4 million from fixed-fee licenses and $11.9 million from variable-fee licenses, compared to $27.0 million in the same period of the prior year, consisting of $14.8 million from fixed-fee