Combine vaccines, infants, and deaths, mix them all up, and you've got one sticky situation. Unfortunately that's where Pfizer (NYSE: PFE) and sanofi-aventis (NYSE: SNY) find themselves after four deaths of infants in Japan.

The country has suspended the use of Pfizer's Prevnar and Sanofi's ActHIB pending an investigation. The infants died after being given the vaccines in combination with other vaccines.

The standard for vaccines sold by Pfizer, Sanofi, GlaxoSmithKline (NYSE: GSK), Novartis (NYSE: NVS) and others is extremely high, since they're preventing disease, rather than treating an illness. When children are involved, that standard goes through the roof.

Both drugs have been used for years. Millions of doses have been given in Japan alone. At this point, I can't see a reason to suspect that there's a problem with the vaccines or their use in combination with others.

One possibility is that there was a bad batch of the vaccines. At least for Prevnar, that seems unlikely, since the deaths appear to have occurred after administration of vaccine from three different lots. It's always possible that multiple lots had an issue, but it should give investors a little confidence that Prevnar isn't to blame.

Even if the vaccines are cleared, the damage is already done. When their children are involved, parents tend to remember warnings more than they do acquittals. Just look at the number of people who still believe there's a link between vaccines and autism, even though it's been long since disproven. Fortunately, doctors -- who tend to be more level-headed -- make recommendations about vaccinations, so it's less of an issue than for over-the-counter medications like Johnson & Johnson (NYSE: JNJ), which is dealing with its own bad press.

When investing in drugmakers, you always have to be worried about safety issues like the ones Merck faced with Vioxx or Wyeth with fen-phen. Fortunately this doesn't look like one of those issues.

Keep track of Pfizer and Sanofi as they deal with this and other issues pertinent to stockholders:

Johnson & Johnson and Pfizer are Motley Fool Inside Value selections. GlaxoSmithKline and Novartis are Motley Fool Global Gains selections. Johnson & Johnson is a Motley Fool Income Investor recommendation. Motley Fool Options has recommended a diagonal call position on Johnson & Johnson. The Fool owns shares of GlaxoSmithKline, and Johnson & Johnson. Motley Fool Alpha owns shares of Johnson & Johnson. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.

Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.