BRUSSELS, July 17 (Reuters) - Europe's second-highest court on Wednesday criticized the European Commission for a lack of transparency over COVID-19 vaccine contracts four years ago, a day before a key vote on Commission head Ursula von der Leyen's bid for a second term.

Some European lawmakers have been highly critical of the Commission's handling of the multibillion-euro contracts, and in particular for not disclosing text messages between von der Leyen and the boss of drugmaker Pfizer about one of the contracts. The Commission says she did not keep the messages.

The Commission signed deals with COVID vaccine supplies AstraZeneca, Sanofi, GSK, Johnson & Johnson, BioNTech, Pfizer, Moderna and others at the height of the pandemic.

Some European Parliament lawmakers asked for access to the documents to understand the terms and contracts. However, the Commission provided only partial access and redacted some of the documents, saying this was done to protect commercial interests and the decision-making process.

The lawmakers took their grievances to the Luxembourg-based General Court and judges on Wednesday upheld their challenge.

"The Commission did not give the public sufficiently wide access to the purchase agreements for COVID-19 vaccines," they said.

"The Commission did not demonstrate that wider access to those clauses would actually undermine the commercial interests of those undertakings," the court added. It also rejected the EU executive's privacy arguments.

The Commission said it would study the court's judgments and their implications and reserve its legal options. It can appeal to the Court of Justice of the European Union, Europe's highest.

The Commission should now be more open about its decision-making procedures after the judgment, said lawmaker Kim van Sparrentak, who together with colleagues took the complaint to the court.

"This ruling is significant for the future, as the Commission is expected to undertake more joint procurements in areas like health and defense," she said.

"The new Commission must now adapt their handling of access to documents requests to be in line with today’s ruling."

The European Parliament is due to vote on Thursday on von der Leyen's bid for a second five-year term.

The European Ombudsman in 2022 accused the Commission of maladministration for not disclosing von der Leyen's text messages with Pfizer chief Albert Bourla.

The New York Times has sued the Commission over its failure to release the text messages.

The cases are T-689/21 Auken and Others v Commission and T-761/21 Courtois and Others v Commission. (Reporting by Foo Yun Chee and Bart Meijer, additional reporting by Piotr Lipinsky in Gdansk; Editing by Mark Potter)