Many investors will likely be wearing big smiles as 2023 winds down. The S&P 500 is on track to deliver a gain of over 20% and could hit an all-time high. The Nasdaq-100 has soared more than 50% and continues to set new record highs.

But not every investor has a reason to be that happy. However, some of them could have brighter days ahead if analysts are right. Here are three stocks down 30% or more this year that Wall Street expects to skyrocket in 2024.

1. BioNTech

BioNTech (BNTX 0.58%) stock has fallen close to 32% this year. That's not surprising, considering that sales of Comirnaty, the COVID-19 vaccine the company co-markets with Pfizer, have plunged. BioNTech's total revenue in the first nine months of 2023 was less than one-fifth of the level from the same period in the prior year.

Wall Street, though, appears to think that a rebound could be on the way for the beaten-down biotech stock. The average analysts' 12-month price target for BioNTech reflects an upside potential of around 36%. The most optimistic analyst projects that the stock could soar more than 150%.

Why do some analysts have such great expectations for BioNTech? It's not because Comirnaty is likely to make a big comeback. Pfizer's recent guidance for 2024 squashed any hopes that would happen.

Instead, BioNTech's pipeline could take center stage and provide potential catalysts. The company has two late-stage candidates -- influenza vaccine BNT161 and cancer immunotherapy BNT316. BioNTech also has 37 other programs in phase 1 and phase 2 testing.

2. JD.com

Shares of Chinese e-commerce giant JD.com (JD 6.12%) have plummeted close to 50% in 2023. China's economy has sputtered. Competition in the country's online shopping market has intensified. JD's growth rate has slowed.

You might think that these factors would cause analysts to throw in the towel on JD, but they haven't -- at least not most of them. Of the 37 analysts surveyed by LSEG in December who cover the stock, 32 recommended it as a buy or a strong buy. Only one analyst recommended selling JD.com shares, with four rating the stock as a hold.

The average 12-month price target for JD is 61% higher than its current share price. Even the most pessimistic price target reflects an upside potential of nearly 8%.

Probably the biggest factor behind the overall bullishness for JD.com is the stock's valuation. JD's shares now trade at a forward earnings multiple of less than 7.9. Many analysts seem to think that this stock has nowhere to go but up.

3. Moderna

Moderna (MRNA 1.69%) has faced similar challenges as BioNTech this year. Sales of its COVID-19 vaccine Spikevax have cratered. As a result, Moderna's share price is down more than 50% year to date.

Some analysts, though, think that Moderna just might make up much its lost ground in 2024. The average 12-month price target for the stock is nearly 50% higher than the current share price.

Moderna has given investors some reasons for optimism. The company and its big partner, Merck, recently announced positive results from a phase 2b study of mRNA-4157 in combination with Keytruda in treating melanoma. The two drugmakers are also evaluating this combo in late-stage trials targeting melanoma and non-small cell lung cancer.

In addition, Moderna hopes to launch its respiratory syncytial virus (RSV) vaccine next year. It's already ramping up for an anticipated commercial launch of the vaccine.

Is Wall Street right about BioNTech, JD.com, and Moderna?

Analysts' price targets aren't always achieved. I'm not sure if Wall Street's bullish views about BioNTech, JD.com, and Moderna will be proven correct next year.

However, I do think the long-term prospects for all three stocks look good. JD.com really is dirt cheap right now. The company remains a major force in the Chinese e-commerce market. BioNTech and Moderna both have promising pipelines beyond COVID-19.

I wouldn't necessarily count on these stocks skyrocketing in 2024 as much as Wall Street projects. But they could deliver market-beating returns for investors over the long run.