Five biotech companies completed initial public offerings during the week of July 22, raising the total number of IPOs in the sector during the past three months to 20, and the year-to-date total to 29.

The performance of the biotech sector over the past two years has been the biggest driver of the boom in IPOs, says John McCamant, editor of The Medical Technology Stock Letter. “They have had a good stretch of earnings and product acquisitions over the last two years,” he says. “The biotech sector has done their job and delivered across the board. It’s created this environment we haven’t had.”

He notes the four biggest biotechs—Celgene, Amgen, Gilead, and Biogen Idec—have led the sector’s strong performance, along with mid-tier companies such as Pharmacyclics, which is up tenfold over the last two years.

After several years of tepid interest from investors and the most promising IPO candidates opting for an acquisition by large pharmaceutical companies, the market for biotech IPOs and follow-on offerings is rolling to a boil from pent up demand. “General investors are willing to buy because they are playing with house money,” McCamant says. “They’ve made more money in biotech over the last two years than people have made in a lot of years before that.”

The 2013 IPO class is also outperforming the general markets, on average up 35 percent from their IPO prices. Three quarters of the issues are trading in positive territory, with four of them—Stemline Therapeutics, Insys Therapeutics, Epizyme, and Prosensa—trading more than 100 percent above their issue price.

Agios Pharmaceuticals, one of the five companies that just completed IPOs, soared 74 percent in its first day of trading and ended the week up 58.5 percent. The biotech raised $106 million after pricing its offering at $18 a share, well above its $14 to $16 a share target range, and increasing the number of shares it offered by 20 percent. Agios’ lead program targeting genetic driven cancer is about to enter the clinic and is partnered with Celgene, which invested $15.3 million in the IPO.

While there are about a dozen biotechs in registration to go public, it’s unclear how many companies are actually on the runway because of a provision in the JOBS Act that allows emerging growth companies to now file confidentially if they choose to do so. It’s likely, though, many more will seek to capitalize on the strength of the public markets to get IPOs done while investors remain receptive.