TIMELINE: The Dengvaxia controversy

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Metro Manila (CNN Philippines) — A vaccine aimed at protecting hundreds of thousands of school children from dengue may have put their lives at risk.

Around 10 percent of over 800,000 students who were immunized with Dengvaxia, but did not have a prior dengue infection, now face contracting a "severe disease," according to the vaccine's manufacturer Sanofi Pasteur.

Following the announcement, the  Department of Health (DOH) halted its nationwide dengue immunization program and has demanded billions in pesos as a refund for the vaccines.

Meanwhile, both Congress and the Justice Department are digging deeper into the controversy, with officials from the current and previous administrations pointing fingers at each other.

Here's how it happened:


Dengvaxia successfully completes its two parallel Phase 3 clinical studies, which compare the safety and effectiveness of the new treatment.

The Philippines was among the 10 countries that took part in the study.

November 9, 2014

Then-President Benigno Aquino III meets Sanofi Senior Vice President in Asia Region Jean-Luc Lowinski at the Philippine Embassy in Beijing, China.

June 9, 2015

Then-Health Secretary Janette Garin negotiates with Sanofi to reduce the cost of buying the vaccines.

October 29, 2015

Sanofi Pasteur applies at the DOH for Dengvaxia to be included in the Philippine National Formulary, a list of drugs that all pharmacies in the Philippines must carry, pending approval by the Food and Drug Administration (FDA).

December 1, 2015

Aquino and Garin meet Sanofi officials during the UN Conference on Climate Change in Paris, France.

December 10, 2015

Garin submits a proposal to the Budget Department to buy three million doses of Dengvaxia.

December 22, 2015

The Philippines grants marketing approval to Dengvaxia, making it the first vaccine to be licensed for the prevention of dengue in Asia.

The Food and Drug Administration (FDA) approves the drug for the prevention of disease caused by all four dengue types in individuals from nine to 45 years old living in high-risk areas.

December 28, 2015

The DOH-Family Health Office submits a request to Garin to exempt Dengvaxia from being included in the Philippine National Formulary. This excludes it from review by the Formulary Executive Council (FEC), which determines what drugs are included on the list.

December 29, 2015

The Budget Department issues a ₱3.5-billion Special Allotment Release Order to Garin's office to purchase the vaccines.

January 21, 2016

The Philippine Children's Medical Center (PCMC) makes a ₱3-billion purchase order for the vaccines without approval from the FEC.

February 3, 2016

Garin issues a Certificate of Exemption for Dengvaxia vaccines to be utilized in the pilot implementation in the National Capital Region, Region III, and Region IV-A.

February 11, 2016

The Philippines, under Health Secretary Janette Garin, hosts the worldwide launch of Dengvaxia.

Read: World's first dengue vaccine now available in PH

March 2016

The World Health Organization (WHO) releases a paper saying Dengvaxia "may be ineffective or may even increase that risk in those who are seronegative at the time of first vaccination."

Seronegative pertains to people who have not yet had dengue.

The WHO calls for more studies into the vaccine.

March 8, 2016

Garin issues a ₱3-billion disbursement voucher to the PCMC to fund the purchase of the vaccines.

March 9, 2016

The PCMC issues its purchase order to Zuellig Pharma, the distributor of Dengvaxia.

April 4, 2016

The government kicks off its ₱3.5-billion, school-based dengue immunization program. The health department says students would be given three doses, which would be administered every six months.

Read: DOH starts dengue vaccination program

July 2016

The WHO releases another paper, saying Dengvaxia "may act as a silent natural infection that primes seronegative vaccinees to experience a secondary-like infection upon their first exposure to dengue virus."

In other words, the body says the vaccine "may be ineffective or may theoretically even increase the future risk of hospitalized or severe dengue illness in those who are seronegative at the time of first vaccination regardless of age."

That same month, former Health Secretary Paulyn Ubial issues a Resolution temporarily suspending the school-based dengue immunization program.

Only the 489,003 pupils who received the first dose would take the second and third doses.

September 2016

The health department moves to continue the vaccination program.

That same month, the Medical Research Council Center FOR Outbreak Analysis and Modelling at Imperial College London releases a study saying Dengvaxia could lead to an increase in the number of cases of the disease if not implemented correctly.

Read: New dengue vaccine could instead cause more cases, experts warn

"Unlike most diseases, the second time you get dengue, it's much more likely to be severe than the first time you get it," said the center's director Neil Ferguson.

October 2016

The Singapore Health Sciences Authority flags "postulated risk" of Dengvaxia.

"As the vaccine is more effective in those who had previous dengue infection, and that there is a postulated risk of severe dengue in those who do not have past dengue infections when they become infected," it said.

November 2016

The House of Representatives probes the allegedly anomalous purchase of the Dengvaxia vaccines.

Its draft report of the Committee on Health, the DOH reported there were 30 cases from March 18 to August 20, 2016 that were "considered as serious cases that needed hospitalization."

Of the three deaths it monitored, two were not related to the immunization program.

The panel directed the DOH to check the medical records of Christine de Guzman who died months after taking the vaccine.

It also recommended that the DOH temporarily suspend the expansion of the vaccination program, pending completion of data collection, evaluation, and analyses on "adverse effects."

Related: House body resumes probe of school-based dengue vaccine program

December 2016

The Senate launches its own investigation into the vaccines, saying the project cost was too big and was approved without congressional approval.

Read: Senate probes dengue vaccine program

November 29, 2017

Sanofi Pasteur announces the results of new clinical data analysis, which found that Dengvaxia is more risky for people not previously infected by the virus.

Read: Drug firm warns of 'severe disease' from dengue vaccine for people with no prior infection

"For those not previously infected by dengue virus, however, the analysis found that in the longer term, more cases of severe disease could occur following vaccination upon a subsequent dengue infection," it said.

"For individuals who have not been previously infected by dengue virus, vaccination should not be recommended," it added.

December 1, 2017

Following Sanofi Pasteur's announcement, Health Secretary Francisco Duque III orders the temporary suspension of the dengue vaccination program.

Read: Gov't halts dengue vaccination program due to health risk

Duque says 733,713 children from Central Luzon, the region of Cavite, Laguna, Batangas, Rizal, and Quezon, and Metro Manila were administered Dengvaxia. Eight to 10 percent or about 70,000 children have not had dengue yet, the DOH added.

December 4, 2017

The Justice Department orders the National Bureau of Investigation to look into the dengue vaccination program.

Read: DOJ orders probe of dengue vaccine program

December 5, 2017

The FDA suspends the sale and distribution of Dengvaxia.

Read: FDA suspends sale, distribution of dengue vaccine Dengvaxia

The WHO says it never recommended to countries the use Dengvaxia in their national immunization programs.

Read: WHO denies recommending Dengvaxia for nat'l immunization programs

December 6, 2017

The health department says more than 800,000 students received the vaccine, up from the 733,713 figure mentioned by Duque.

It is now monitoring 40 cases of children who fell seriously ill, up from 30 in 2016, and nine deaths.

Read: DOH: More than 800,000 children vaccinated with Dengvaxia

December 7, 2017

The Health Department says it will return around 800,000 leftover Dengvaxia vaccines, worth P1.4-billion, to Sanofi.

Read: Health Department to return ₱1.4 billion worth of Dengvaxia vaccines

December 8, 2017

The health department calls for a refund of the P3.5 billion it paid for the vaccines, adding it has created a task force to look into the program.

Read: DOH to demand from Sanofi full refund of P3.5 billion spent on Dengvaxia

That same day, the House and the Senate announce they will again investigate the dengue vaccination program. It begins on Monday, December 11.

Read: Senate to open probe on dengue vaccine scare

December 11, 2017

The Senate starts its probe into the Dengvaxia issue. Former Health Secretaries Janette Garin and Paulyn Ubial, as well as Health Secretary Francisco Duque III and Sanofi officials, are among those present.

Before the start of the hearing, former Health Secretary Enrique said Garin, his successor, was "solely responsible" for the Dengvaxia issue.

Read: Ex-DOH Sec. Ona: Garin solely responsible for Dengvaxia 'nightmare'

Meanwhile, Garin says the purchase of the vaccines was "above board."

Read: Ex-DOH Secretary Garin: No corruption in Dengvaxia purchase

December 14, 2017

Aquino, under whose administration the deal was approved, attends the Senate hearing on the vaccine program.

Aquino claims no one advised him against procuring Dengvaxia, with health reform advocate Dr. Anthony Leachon saying that the former President cannot be faulted if he was given "misleading" information on Dengvaxia.

Read: Ex-President Aquino: No one advised me against Dengvaxia

Presidential Spokesperson Harry Roque says that President Rodrigo Duterte believes the program was done "in good faith," adding that Duterte would have done the same.

Read: Duterte thinks Dengvaxia purchase done in 'good faith' - Roque

Meanwhile, Ubial reveals that Garin's husband, Rep. Oscar Garin Jr., pressured her to continue the roll out of the vaccine program.

Read: Ex-DOH Sec. Ubial: Janette Garin's husband asked me to buy more Dengvaxia

January 19, 2018

At an event in San Fernando, Pampanga, Health Secretary Francisco  Duque III confirmed Sanofi Pasterur has refunded P1.16 billion worth of unused Dengvaxia vaccines.

However, Duque clarified the reimbursement does not put the French pharmaceutical company off the hook, adding the investigation continues on whether Sanofi withheld significant information on possible risks.

READ: Sanofi refunds P1.16-B for unused Dengvaxia vaccines

For questions or concerns regarding the Dengvaxia program, you may call the DOH at 711-1001 or 711-1002.

This is a developing story. Please refresh the page for updates.

CNN Philippines Digital Producer VJ Bacungan and Senior Researcher Ella Hermonio contributed to this report.