There’s one concern dominating the minds of investors at the moment and that’s Brexit. Indeed, if Britain votes to leave the EU on 23 June, the country will be subject to a multi-year period of uncertainty, and it’s this uncertainty that will cause investors the most pain.

To protect against uncertainty and any adverse effects that may come as a result of Britain’s decision to leave the EU, investors could look to large international firms with well-covered dividend yields and well-positioned to succeed in any economic environment.

Defensive business 

GlaxoSmithKline (LSE: GSK) is one such company. The pharmaceuticals giant is a world leader in the production of consumer pharmaceutical products, such as over-the-counter medicines, toothpaste and painkillers. What’s more, the group has a large vaccines division as well as a stake in ViiV Healthcare, a joint venture dedicated to delivering advances in treatment and care for people living with HIV. It’s extremely unlikely that any one of these businesses will see a sudden drop-off in demand for their products in the event of a Brexit.

Moreover, this year Glaxo is on track to report its first year of earnings growth since 2011, so there’s already a significant amount of positive sentiment surrounding the group. City analysts expect the company to report earnings growth of 16% this year, followed by growth of 5% for 2017.

Management has already come out to confirm it’s on track to meet this target. In fact, the first quarter of 2016 was one of the most impressive in several years for the company. Sales increased by 11%, to £6.2bn and earnings per share, excluding exceptional items and adjusted for currency, rose 8% to 19.8p. Shares in Glaxo currently trade at a forward P/E of 15.9 and support a dividend yield of 5.7%.

Global oil company 

Royal Dutch Shell (LSE: RDSB) is another large international company that’s unlikely to be significantly affected by a leave vote. As one of the largest oil traders in Europe and one of the biggest integrated oil companies in the world, Shell is a vital part of the global economy. 

This means that the group is likely to continue to churn out returns for investors no matter what the future holds for the UK economy.

Over the next few years, Shell’s earnings should climb steadily higher as the company continues its integration of recently acquired BG Group and cuts costs further to deal with the slump in oil prices. Asset sales should bolster the enlarged group’s balance sheet while improving margins as low-return assets are sold off.

Shares in Shell currently trade at a forward P/E of 23.7 and support a dividend yield of 7.2%. Management has announced its commitment to the dividend for the foreseeable future so a payout should be secure no matter what the outcome on 23 June.

Income champion 

If it's income you're after, our analysts have discovered a company we believe is one of the market's dividend champions. All is revealed in the Motley Fool's new income report, titled A Top Income Share From The Motley Fool. It gives a full rundown of the company, its prospects and our reasons for buying. 

This is essential reading for income investors.

The report is completely free and will be delivered straight to your inbox. Click here to download the free report today!

Rupert Hargreaves owns shares of GlaxoSmithKline and Royal Dutch Shell B. The Motley Fool UK owns shares of and has recommended GlaxoSmithKline. The Motley Fool UK has recommended Royal Dutch Shell B. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.