After plunging more than 19% last year, the S&P 500 is off to a good start in 2023. It's the opposite story, though, for Johnson & Johnson (JNJ -0.46%): Shares of the healthcare giant rose 3% in 2022 but have declined so far this year.

Even better-than-expected guidance for the new year in J&J's fourth-quarter update on Tuesday failed to make investors happy. However, I think there's a good chance that Johnson & Johnson stock could rebound after a bad start in 2023. Here are three reasons why.

1. Declining COVID-19 impact

The impact of COVID-19 continued to weigh on Johnson & Johnson in its latest quarter. The company reported Q4 sales fell 4.4% year over year to $23.7 billion. One of the two factors behind this decline was lower COVID-19 vaccine sales.

No, Johnson & Johnson isn't likely to experience a significant sales bounce with its COVID vaccine. However, the year-over-year comparisons should get better in 2023.

Lower vaccine revenue wasn't the only COVID-related issue for J&J, though. COVID presented a headwind for sales of the company's pulmonary hypertension drugs and for its medtech business (especially in China). 

However, the worst could now be over. A top Chinese government epidemiologist even stated recently that the chances of a major COVID rebound in China within the next three months are low because so many people in the country have already been infected.

2. Potential for a weaker U.S. dollar

Unfavorable foreign exchange rates stood out as the other big factor behind Johnson & Johnson's Q4 sales decline. The company said that its Q4 sales actually rose slightly year over year on a constant-currency basis.

These foreign exchange headwinds are due to the strong U.S. dollar. And the strength of the dollar is in part the result of the Federal Reserve's aggressive interest rate hikes.

The strong dollar hurts J&J because nearly half of its sales are in international markets. Johnson & Johnson receives payment in other currencies but must convert them into U.S. dollars for financial reporting. This conversion results in weaker sales when the dollar is strong.

There could be some good news on the way, though. The Fed seems likely to make smaller interest rate increases going forward. Some economists predict that rate cuts could be in store in the second half of 2023. 

This could mean that the U.S. dollar will weaken somewhat later this year. If so, Johnson & Johnson's reported sales and earnings could be higher than expected.

3. Upcoming spinoff

On an adjusted operational basis (which excludes the impact of translational currency, acquisitions, and divestitures), Johnson & Johnson's overall sales increased by 6.2% in 2022. The company's pharmaceutical segment grew at a little faster rate of 6.8%. Its medtech unit grew at a slightly slower rate of 6.1%.

Then there's consumer health. Adjusted operational sales for the segment rose by 3.9%, well below J&J's other two major business units. Clearly, consumer health is holding back the company's overall growth.

But Johnson & Johnson plans to spin off the consumer health unit later this year. My Motley Fool colleague Alex Carchidi recently referred to this milestone as a "once-in-a-decade buying opportunity" for J&J stock. You could even argue that "once in a decade" doesn't do justice to the opportunity, since Johnson & Johnson has never done such a major spinoff in the past.

Regardless of how you describe it, I think that J&J's consumer health spinoff is a good move. Johnson & Johnson will be a nimbler, faster-growing company with its new focus only on pharmaceuticals and medtech, and the upcoming spinoff could provide a nice catalyst for J&J stock.

The wild card

Is it a slam dunk that Johnson & Johnson stock will rebound after its inauspicious start to 2023? No. The big wild card, in my view, is the status of the global economy. A severe recession would likely pull most stocks down -- potentially including J&J.

However, Johnson & Johnson would almost certainly fare better than the overall market would in an economic downturn. The company is a Dividend King with a resilient business model that's survived and thrived for a long time. Investors have seen J&J as a safe haven in the past. I don't expect this would change if there's a recession this year.

That said, it's still possible that a recession isn't on the way. The odds that Johnson & Johnson stock will bounce back after its weak start this year should be much better in a stronger economy. Either way, I think that J&J has what it takes to deliver market-beating returns in the long run.