What happened

It's Tuesday, and e-commerce stocks are sinking again. For the second day in a row, shares of MercadoLibre (MELI -1.35%), the Argentine eBay, Sea Limited (SE -0.90%), its Singaporean peer, and Chewy (CHWY 2.80%) -- a somewhat more focused e-commerce play that caters to pet owners -- are dropping, down 5.4%, 4.4%, and 5.8%, respectively -- and apparently, on no relevant news.

Well, not no news, exactly. While there's a dearth of usual suspects today -- no analyst downgrades or price target cuts, no bad earnings reports, nor preannouncements of same -- e-commerce stocks continue to suffer the ill effects of Pfizer's announcement yesterday that its coronavirus vaccine candidate is 90% effective.

3 arrows trending down over a background of a map and chart points

Image source: Getty Images.

So what

But isn't that good news? Well, in a sane world, certainly. The potential for Pfizer to have a safe and effective vaccine for COVID-19 promises to release consumers from their homes around the world and permit them to rejoin the global economy, venturing out, eating out, seeing entertainment in a crowd, and shopping with abandon (and in person).

Problem is, that's not necessarily good news for companies that do most of their business online.

It's largely because of coronavirus-related shutdowns (and the stay-at-home orders it spawned) that Chewy's sales surged 47% year over year last quarter, while MercadoLibre's business got 61% bigger and Sea Limited literally doubled in size -- sales were up 102% year over year, in fact.

Now what

Now investors are beginning to wonder: If Pfizer's vaccine is as good as advertised, will consumers continue to order online and have their purchases shipped directly to their doors once that is no longer the only option? Or will they abandon the ease of e-commerce and want to go back to shopping in person?

Personally, I think the answer to this question is glaringly obvious: Shopping online is easier, and easy is good.

The market share increases and sales gains these companies have made during the crisis will not soon go away. That doesn't necessarily mean, of course, that MercadoLibre stock is any kind of a bargain at 2,900 times trailing earnings. It doesn't mean you should feel entirely confident buying Sea Limited or Chewy, either -- not with both of those companies still mired in red ink and losing money on every sale they make.

But it does suggest the possibility that investors, who abandoned their shares of Chewy, MercadoLibre, and Sea Limited stocks yesterday, and who are doing so again today, might be seeing the future wrong and acting impulsively because of it.