The World Health Organization (WHO) declared that the H1N1 pandemic has entered the post-pandemic period on August 10, 2010.WHO stressed that this does not mean the pandemic H1N1 virus has disappeared and the virus will continue to circulate like the seasonal influenza virus for years to come, resulting in outbreaks of different sizes.In addition, WHO urged continued vigilance and implementation of measures against the H1N1 virus, including surveillance and reporting for the H1N1 virus, provision of influenza vaccine and prompt administration of antiviral drugs to high risk groups and patients with severe influenza.In the meantime, it is imperative for the Taiwan Centers for Disease Control (Taiwan CDC) to review its response to the 2009 H1N1 pandemic. The review is as follows.

1. Current influenza activity in Taiwan:
Since the beginning of the 2009 H1N1 pandemic, a total of 47 deaths resulted from H1N1 infection have been confirmed in Taiwan.Approximately, 800,000 people have been infected with the virus.According to the multiple surveillance systems set up by Taiwan CDC, the weekly number of outpatient visits for influenza-like illness (ILI) during the first week of August, 2010 was 60,283 and 1.16% of these patients were confirmed to have influenza, which is 4% higher than that during the previous week (1.12%).During the recent 3 weeks, the percentage of specimens tested positive for influenza virus was about 21%.Among these specimens, 49% were tested positive for influenza A (H3N2) virus, 28% were tested positive for influenza B virus, and 23% were tested positive for the 2009 pandemic influenza A (H1N1) virus.As a result, the weekly number of new cases of seasonal influenza is estimated to be 9,748 and the weekly number of new cases of the 2009 pandemic influenza A (H1N1) virus infection is estimated to be 2,912.Based on all the surveillance data, the overall intensity of seasonal influenza activity is moderate.The dominant circulating seasonal influenza virus is influenza A (H3N2).On the other hand, the overall intensity of the 2009 pandemic influenza A (H1N1) activity is low and not as severe as that during the last year.Nevertheless, H1N1 still poses threat to those who are not vaccinated against it. Hence, Taiwan CDC urges clinicians to encourage the public to get vaccinated against H1N1 to protect their health and the health of others.

2. H1N1 vaccine safety surveillance:
To ensure the safety of the H1N1 vaccine, the Department of Health (DOH) continues to monitor vaccine adverse events.Thus far, 9.12 million doses of the H1N1 vaccine have been distributed. According to the latest surveillance data, as of August 3, 2010, the reporting rate of adverse events per 100,000 doses distributed in Taiwan is 15.4, which is lower than that in Canada, 25.9 per 100,000 doses distributed, but higher than that in the U.S., 8.8 per 100,000 doses distributed.The reporting rate of serious adverse events (an event that results in death, is life-threatening, requires inpatient hospitalization, results in persistent disability, prolongs the existing hospitalization, or is a birth defect) in Taiwan is 4.5 per 100,000 doses distributed, which is higher than that in both Canada and the U.S., 1.1 per 100,000 doses distributed and 0.7 per 100,000 doses distributed, respectively.Nevertheless, several factors should be taken into account when comparing the reporting rates of serious adverse events in Canada, Taiwan and the U.S., for instance, Taiwan’s National Health Insurance that increases the access to timely and quality health care services and media reports that influence public confidence in the vaccine.Prior to the H1N1 vaccination campaign that began last year, DOH has established the National Health Insurance Database to monitor trends in the incidence of diseases.When no vaccination is involved, on average, 9 cases of autoimmune nerve disorder, including Guillain–Barré syndrome (GBS), 389 cases of Bell’s palsy, 1,532 cases of stroke/brain attack, 745 cases of myocardial infraction, and 46 cases of immune thrombocytopenic purpura are reported in Taiwan every week.In addition, in Taiwan, 13 out of 100 recognized pregnancies end in miscarriage and 1 out of 100 recognized pregnancies ends in fetal death.A total of 5.68 million doses of the H1N1 vaccine had been administered.Based on the number of the H1N1 vaccine administered, the reporting rate of adverse events per 100,000 doses administered in Taiwan is 24.8 and the reporting rate of adverse events per 100,000 doses administered in Taiwan is 7.2.With regard to different brands of the H1N1 vaccine, the reporting rate of adverse events per 100,000 doses of vaccine manufactured by Adimmune is 23.2 and the reporting rate of adverse events per 100,000 doses of vaccine manufactured by Novartis is 26.3.Further, the reporting rate of serious adverse events per 100,000 doses of vaccine manufactured by Adimmune is 7.3 and the reporting rate of serious adverse events per 100,000 doses of vaccine manufactured by Novartis is 5.4.All of the above-mentioned reporting rates of adverse events do not exceed the normal range when no vaccine is administered.

At the time of writing, the Vaccine Injury Compensation Program (VICP) has received a total of 533 claims requesting compensation for individuals thought to be injured by the 2009 pandemic influenza A (H1N1) vaccine. VICP has completed reviewing 288 petitions.249 cases were ruled non-compensable while the other 39 cases were ruled compensable (association is confirmed in two cases, including itchy skin rashes and rhabdomyolysis, while association cannot be excluded in the other 37 cases, including vasculitis, immune thrombocytopenic purpura, itchy skin rashes, neural hearing loss, acute spinal cord injury and myelitis, GBS, acute encephalitis, and acute disseminated encephalomyelitis).A total of 47 suspected vaccine-related deaths were filed for compensation.46 cases have been reviewed and ruled non-compensable, and the other one case is waiting for the autopsy results.

3. Role of vaccine in influenza control:
As the saying goes, “An ounce of prevention is worth a pound of cure”.Vaccination is the single most effective preventive measure against H1N1.In Taiwan, the H1N1 vaccination rate among persons aged 19-24 years is merely 4%.Recently, several clusters of H1N1 cases have been reported in newly enlisted soldiers.Further, many young, healthy adults who became infected with the 2009 influenza A (H1N1) have either passed away or been receiving long-term treatment in the intensive care unit.Among the 47 people who have died of H1N1 infection, only one had received the vaccination prior to disease onset.The 2009 influenza A (H1N1) vaccine purchased by the government last year is about to expire in November, 2010.Further, young, healthy adults are not included in the priority list for the 2010 seasonal influenza vaccination campaign.If the H1N1 virus becomes active again in this fall and winter, young, healthy adults will only be able to get the self-paid seasonal influenza vaccine.Moreover, by then, there might not be enough seasonal influenza vaccine for everyone.Therefore, young, healthy adults are urged to receive the 2009 influenza A (H1N1) vaccine now to protect their health.

4. Antiviral drug use strategies:
In Japan and the U.S., antiviral drugs are prescribed to patients with poor immunity and suspected influenza.In the other countries in the world, antiviral drugs are not prescribed as commonly.Additionally, antiviral drugs in most other countries are either self-paid or covered by insurance.On the other hand, Taiwan has adopted slightly different antiviral drug use strategies.Based on the national health insurance data and community-based virus surveillance data collected in the past years, Taiwan CDC estimated that the number of patient visits for influenza-like illness for 2010-11 to be 1.6 million and the number of patient visits for influenza infection to be 260,000.If we were to prescribe antiviral drugs to all patients with influenza-like illness, approximately 1.34 million treatment courses of antiviral drugs will go to waste.Therefore, Taiwan CDC has promulgated that the antiviral drugs funded by the government are currently targeted for treatment of persons who are cluster cases in institutions or hospitalized patients with suspected severe influenza complications.

5. Diagnostic testing services for influenza:
Although influenza RT-PCR tests are comparatively sensitive, the average number of specimens collected from patients with influenza-like illness to be tested every week, 60,000 , far exceeds the laboratory capacity of the ten contracted laboratories and Taiwan CDC’s laboratory, which is 5000.The cost of each influenza RT-PCR test is about NT$1,300.Each week, it may cost up to about NT$78 million to test all the specimens received. Therefore, influenza RT-PCR tests are not funded in most countries in the world.In Taiwan, influenza RT-PCR tests for patients with suspected severe influenza complications are funded by the government and conducted by the ten contracted laboratories and Taiwan CDC’s laboratory.In comparison, rapid diagnostic tests for influenza are less sensitive.As a result, such test is not government-funded in most countries.The test is also currently not funded by the Taiwanese government. Nevertheless, clinicians in Taiwan are advised to recommend self-paid antiviral drugs to patients who need the drugs, but have not met the requirements for use of antiviral drugs funded by the government.

Conclusion:
On August 5, 2009, the Influenza Advisory Committee under DOH called a consultation meeting.The participating experts agreed with Taiwan CDC on its current H1N1 vaccination policy.Hence, no changes will be made to the policy unless when necessary.With regard to influenza control, Taiwan CDC has put the available budget into efficient use, including providing government-funded vaccines, influenza tests and antiviral drugs to targeted population.Nonetheless, Taiwan CDC will continue to re-examine and review its strategies and policies in order to ensure the health of the people in the nation.However, we all know effective disease control is not possible without the support of clinicians and the public.Clinicians are once again urged to encourage the public to get vaccinated against influenza as well as to promptly diagnose and prescribe government-funded antiviral drugs to patients with suspected severe influenza complications or cluster cases in institutions.Additionally, clinicians are urged to report such cases to the local health bureau immediately and have specimens collected from the cases to be tested at either one of the ten contracted laboratories or Taiwan CDC’s laboratory.The result of the influenza RT-PCR test will be ready in about 24 hours.Finally, I would like to thank you all for your cooperation in ensuring the health of the people in our nation.

Feng-Yee Chang, MD, PhD
Director-General
Taiwan Centers for Disease Control