Looking closer at the option chain at ISE.com I saw two large transactions occur: 20,000 PFE June 2010 $18 Calls traded at 0.27 and 20,000 PFE January 2011 $20 Calls traded at $1.06. The underlying price is at $17.14. I'm not sure if these were the "opening" transactions, but they were traded on the ISE exchange. I'm also not sure of the nature of the trades and the volume was way under open interest. According to this Schaeffers Research article, PFE calls were also active during the previous session. PFE implied volatility (23.56) is higher than historical volatility (15.75). PFE along with XLV and the S&P 500 will be something to watch.
In the end the only thing that matters is the chart. It is riding the 200 day moving average (16.95) and 38.2% Fibonacci retracement level and has been in a downtrend since January. A trend reversal or 200dma breakdown would be something to monitor.
PFE 2 year chart (Courtesy of Stockcharts.com)
$PFE 6 month chart
Also watch the XLV health care ETF. If it rolls over here it could retrace a bit and bring PFE with it. It needs to break above $33 resistance.
XLV 2 year chart (Courtesy of stockcharts.com)
I found a Pfizer research report by Ockham Research. They think the stock is undervalued based on expected sales growth this fiscal year and PFE's price/sales, price/cash ratios are trading well below the historical range. They lose patent protection on Lipitor in 2011 so the multiples could be pricing this in [read the research report here].