What happened

BioNTech (BNTX -1.80%) shares were having an atypically bad day on Wednesday, and by the close of trading were down by nearly 7%. A downshift in one analyst's recommendation seems to be the latest headwind buffeting the company's stock.

So what

Analyst Simon Baker at Redburn Securities changed his recommendation on the stock to sell from neutral, tagging it with a $146 per share target price. That's nearly 30% below its current level.

Child receiving a vaccine shot while being comforted by an adult.

Image source: Getty Images.

His reasoning, detailed in a research note published Wednesday, is that the sturdy gains the stock has enjoyed since the end of March are not justified by the biotech's most recent guidance or by the considerable revenue the company still stands to take in from the coronavirus vaccine it developed in partnership with Pfizer (PFE -2.63%).

Wednesday's investor bearishness was also related to Monday's news from Novavax. The vaccine specialist announced stunningly positive phase 3 clinical trial results for its NVX-CoV2373 COVID-19 vaccine candidate. They showed more than 90% efficacy overall, and 100% against moderate and severe instances of the disease.

Now what

So basically, it's been a tough week for BioNTech, which perhaps seems as if it's becoming yesterday's coronavirus vaccine news. Yet the pandemic is far from over, and the BioNTech/Pfizer jab is one of the best in class. Meanwhile, the messenger RNA (mRNA) technology used in that shot is only in its beginning stages, promising a bright future for BioNTech -- which has a wide pipeline stuffed with mRNA-based products.