The world’s largest credit ETF has ballooned since the Federal Reserve said it will backstop the market.

Total assets in BlackRock’s iShares iBoxx $ Investment Grade Corporate Bond exchange-traded fund, ticker LQD, touched a record $46.7 billion on Tuesday, according to data compiled by Bloomberg. That compares to $28.2 billion on March 19, just days before the central bank said it would purchase investment-grade corporate bonds and certain ETFs that tracked them.

The Fed’s move spurred a rally in high-grade bond markets, where investors were shedding their holdings in an effort to raise cash amid dire economic data. The central bank’s pledge combined with the asset class’s strong fundamentals makes investment-grade bonds look appealing, according to Columbia Threadneedle’s Ed Al-Hussainy.

“Investment-grade credit is particularly attractive at the moment -- it captures large corporates with solid balance sheets and good access to market financing to weather this recession,” said Al-Hussainy, a senior strategist at the firm. “And of course, the asset class has an explicit Fed backstop.”

LQD has rallied since the Fed announced the Secondary Market Corporate Credit Facility on March 23, which kicked off its first purchases last week. Corporate-debt funds led the intake for fixed-income ETFs last week, with investment-grade funds posting inflows and high-yield funds seeing outflows.

The Fed’s touch has also been felt in the junk-bond market, with BlackRock’s iShares iBoxx High Yield Corporate Bond ETF, ticker HYG, also hitting a record size of $21.7 billion this week. U.S. policy makers expanded the bond-buying program to include recently downgraded debt last month, though the “preponderance of ETF holdings” will be concentrated in funds tracking high-grade credit.

In addition to the Fed’s backstop, the economy’s reopening should benefit small-cap stocks and junk bonds, which tend to have weaker balance sheets, according to Academy Securities.

“For me, it’s all about the reopen and a ‘rotation’ from work-from-home,” said Peter Tchir, Academy’s head of macro strategy. “High-yield does well generally when small caps do, so the upside will be in high-yield and leveraged loans.”

But for Columbia’s Al-Hussainy, betting on junk bonds is still too risky of a proposition at this stage.

“Right now, I would say investment-grade offers best risk/reward as a bet on the Fed’s balance sheet,” Al-Hussainy said. “Equities and high-yield are a bet on the effectiveness of fiscal policy.”