Better-than-expected COVID-19 vaccine sales pushed Moderna past Wall Street’s second-quarter forecasts.

The company said that its Spikevax vaccine brought in US$4.53 billion during the quarter. Analysts were looking for around US$3.6 billion, according to FactSet.

Moderna shares surged Wednesday after the company also announced another US$3 billion share buyback plan.

Moderna’s vaccine sales in the second quarter represent a drop from the nearly US$6 billion that the vaccine brought in during the year’s first quarter, when a virus surge through the United States (US) pushed more people to seek protection.

But those sales could pick up again later this year.

Moderna has developed an updated version of its vaccine for a fall booster campaign that combines the original shot with protection against the omicron variant.

The company announced last week that it reached a deal with the US government for an initial purchase of 66 million doses of the booster shot for up to US$1.74 billion. The government also has an option to purchase more doses.

The COVID-19 vaccine is Moderna’s main source of revenue, outside of grants and money from collaborations. Total revenue climbed nine per cent in the second quarter to US$4.75 billion.

But operating expenses also swelled 78 per cent to US$2.3 billion for the vaccine maker, which has several products in late-stage clinical trials, the most expensive phase of research.

Moderna had $499 million in inventory write-downs in the quarter tied to vaccine doses that exceeded or were expected to exceed their shelf lives before being used. The company also said it booked another loss and an expense for unused manufacturing capacity due partly to a “substantial reduction” in expected deliveries to the COVAX vaccine-sharing program.

Overall, net income plunged 21 per cent to US$2.2 billion in the second quarter, and earnings totaled US$5.24 per share.

Analysts expected earnings of US$4.58 per share on about US$4.1 billion in revenue, according to FactSet.

Moderna said Wednesday that its board authorised an additional US$3 billion share repurchase program to return capital to shareholders. The company has repurchased 16 million shares since last year’s final quarter. It still has about US$1 billion left on another US$3 billion repurchase program it announced in February.

Shares of Cambridge, Massachusetts-based Moderna Inc. jumped more than 15 per cent in midday trading to US$185.83 while broader indexes climbed over one per cent.