What happened?

Pharma giant Merck (MRK -0.14%) released a disappointing first-quarter 2021 earnings report on Thursday, and as a result, the company's stock took a bit of a dive today. The drugmaker's shares were down by 4.96% at the close of the day's trading session, after falling by as much as 5.5% earlier in the day.

So what

Merck's results were unimpressive in more ways than one. The company's sales came in at $12.1 billion, which more or less remained flat compared to the first quarter of the previous fiscal year. Meanwhile, Merck's adjusted earnings per share (EPS) was $1.40, representing a 7% decline compared to the year-ago period. Analysts tracking the company had predicted that on average, it would report revenue of $12.66 billion and adjusted EPS of $1.63.

Pills arranged in the form of a question mark.

Image source: Getty Images.

In other words, the pharma giant's results came in far short of analyst estimates -- on both the top and bottom lines. That's a recipe for disaster for any company. It is no wonder that investors sent Merck's stock tumbling today. Why did the healthcare company fail to deliver during the first quarter? Among other things, Merck blamed the continued fallout of the COVID-19 pandemic. According to the drugmaker, the negative impact of the outbreak on its top line during the first quarter amounted to roughly $600 million.

Now what

Merck's guidance for the full fiscal year 2021 was a bit more encouraging. On the top line, the company expects revenue between $51.8 billion and $53.8 billion. At the midpoint, this guidance would top the average analyst estimate of $52.5 billion. Merck also thinks it will record adjusted EPS between $6.48 to $6.68 during the current fiscal year, which at the midpoint is just slightly below the $6.57 adjusted EPS analysts are predicting.