$hot in the arm; Drugstores dive deeper into flu vaccines.

• Author: Murphy, Tom
• Position: Business

Byline: Tom Murphy

Walgreen provided enough flu shots last season to protect a population roughly twice the size of Los Angeles.

CVS doled out more than 5 million, or double its total from a few years ago. And Wal-Mart, the world's largest retailer, offers flu shots at more than 4,200 of its U.S. stores that have pharmacies.

The nation's biggest drugstores and other retailers are grabbing larger chunks of the immunization market, giving customers more convenient options outside the doctor's office to protect themselves against the flu, pneumonia and other illnesses. In fact, nearly half of all flu vaccines provided to adults are now administered in nonmedical settings like drugstores or worksite clinics.

But this push by retailers muscles into an area of health care that was once largely the domain of the family doctor. And that stirs some concern from doctors who want to stay tuned into the health of their patients and keep track of who has received a vaccine.

Doctors often use flu shot appointments to ask patients about chronic conditions such as diabetes they may be treating, said Dr. Robert Wergin, a family physician in Milford, Nebraska, and president-elect of the American Academy of Family Physicians.

''That relationship, knowing the patient, that's important,'' he said, adding that many doctor offices have worked to become more convenient by offering same-day appointments for flu shots.

Retailers say their pharmacists can notify a customer's primary care doctor that the patient had a flu shot, if the patient gives them the contact information, and their expansion into vaccinations isn't meant to replace a primary care doctor visit.

''It's all about providing our customers with access to affordable health care,'' said Danit Marquardt, a Wal-Mart spokeswoman.

Retailers, some of which also offer vaccinations against diseases such as yellow fever and chickenpox, don't disclose how much they make off vaccines. They likely represent a small slice of overall profit, but their value extends beyond what they contribute to the bottom line.

''The vaccine is, I think ... a good marketing tool to bring people in,'' said Eric Keuffel, a Temple University health economist.

The first flu shot Lynn Bruggemann got was an impulse purchase she made in 2011 while visiting a CVS store to buy toothpaste and shampoo. It took about 15 minutes and...