Shares of Abbott /zigman2/quotes/203724446/composite ABT -1.60% fell 2.3% in premarket trading on Tuesday after the diagnostics company updated its financial outlook for 2021, citing declining demand for its COVID-19 tests. Abbott said it now expects earnings per share of $2.75 to $2.95 and adjusted EPS of $4.30 to $4.50. The company in April said it projected EPS of at least $3.74 and adjusted EPS of at least $5.00 for the full year. There are a number of reasons why COVID-19 testing volume is declining in the U.S., including increasing vaccination rates and recent guidance from the Centers for Disease Control and Prevention that told vaccinated Americans they do not need to get tested if they are exposed to someone infected with the virus. Abbott has developed 12 COVID-19 tests, which generated $2.2 billion in the first quarter of the year. Abbott's stock is up 6.5% for the year, while the broader S&P 500 /zigman2/quotes/210599714/realtime SPX +0.28% has gained 11.9%.