Health care is a recession-proof sector, since folks will continue to take their medications no matter how bad the market gets. However, it’s important to understand that some of the biggest names in Big Pharma continue to struggle under the weight of looming patent expirations — companies like Pfizer (NYSE:PFE), Merck (NYSE:MRK) and others. That’s why health care investors should consider up-and-coming biotech stocks as part of their portfolio. These biotechnology companies could be working on tomorrow’s blockbuster drug, not profiting from an old idea that will soon be out of their patent protection.

I watch more than 5,000 publicly traded companies with my Portfolio Grader tool, ranking companies by a number of fundamental and quantitative measures. This week I’ve got 9 booming biotech stocks to buy.

Here they are, in alphabetical order. Each one of these stocks gets an “A” or “B” according to my research, meaning it is a “strong buy” or “buy.”

Alexion Pharmaceuticals Inc. (NASDAQ:ALXN) develops and commercializes products for hematology, neurology, ophthalmology and cancer. Like other pharmaceutical products that continue to soar during the recession, ALXN is up 64%, year-to-date.

Alkermes (NASDAQ:ALKS) is an integrated biotechnology company that attempts to treat prevalent, chronic diseases. Since the start of 2011, ALKS stock has gained 36%, compared to small gains by the broader markets.

Biogen Idec Inc. (NASDAQ:BIIB) is a biotechnology company that works with neurological disorders and other serious diseases. BIIB stock has jumped an impressive 75%, proving that pharmaceutical stocks can thrive during a down economy.

BioMarin Pharmaceutical Inc. (NASDAQ:BMRN) develops and commercializes pharmaceuticals including Naglazyme, Kuvan and Aldurazyme. BMRN has taken the lead of other Big Pharma stocks by gaining 18% year-to-date.

Cepheid (NASDAQ:CPHD) is a molecular diagnostics company that develops products for the clinical market. A 57% gain, year-to-date, for CPHD stock has left stockholders pleased with their purchase.

Curis Inc. (NASDAQ:CRIS) is a drug discovery company that develops target cancer therapies. CRIS stock is one of the big winners on this list, gaining 78% in just 10 months.

Nymox Pharmaceutical Corp. (NASDAQ:NYMX) is a biopharmaceutical company that markets an aid for the diagnosis of Alzheimer’s disease. NYMX stock has gained 27%, compared to much smaller gains by the broader markets.

Opko Health Inc. (AMEX:OPK) is a diagnostics and pharmaceutical company that focuses on molecular diagnostics tests, pharmaceuticals and vaccines. An impressive year-to-date return of 23% for OPK stock ensures a spot on this list.

Spectrum Pharmaceuticals Inc. (NASDAQ:SPPI) is a commercial stage biopharmaceutical company working primarily with hematology, oncology and urology. SPPI stock is up 31% year-to-date, compared to a gain of just 2% for the Dow Jones.

Get more analysis of these picks and other publicly-traded stocks with Louis Navellier’s Portfolio Grader tool, a 100% free stock-rating tool that measures both quantitative buying pressure and eight fundamental factors.