Charlot Zahra analyses the different vaccines and medication used to combat the Influenza A virus subtype H1N1 (aka swine Flu) in Malta
The vaccine being utilised in Malta to vaccinate A-H1N1 patients is Pandemrix, which reportedly offers protection against mutations of the A-H1N1 virus.
About 100,000 doses for Pandermix were shipped to Malta early last week and started being utilised immediately to inoculate health workers and those in a higher-risk category, such as pregnant women, people suffering from chronic illnesses, children under five and those over 60.
However, doctors are advising all those who they deem needs vaccination to actually take the vaccination after a medical certificate is issued.
The vaccine was developed by GlaxoSmithKline and patented in September 2006.
The vaccine is one of the A-H1N1 vaccines approved for use by the European Commission in September 2009 upon the recommendations of the European Medicines Agency (EMEA).
As well as the active antigen derived from A/California/7/2009 (A-H1N1), the vaccine contains an immunologic adjuvant AS03 which consists of DL-α-tocopherol (vitamin E), squalene and polysorbate 80.
Thiomersal (thimerosal) is added as a preservative.
Being manufactured in chicken eggs, it contains trace amounts of egg proteins. Additional important non-medicinal ingredients are formaldehyde, sodium deoxycholate, and sucrose.
Whilst other 2009 A-H1N1 vaccines have been developed, the use of a proprietary immunologic adjuvant was claimed to boost the potency of the body’s immune response, meaning that only a quarter of the inactivated virus is needed.
Professor David Salisbury, Head of Immunisation at the UK Department of Health said the vaccines with adjuvants offered good protection even if the virus changed over time.
“One of the advantages with adjuvanted vaccines is their ability to protect against drifted (mutated) strains. It opens the door for a whole new strategy in dealing with flu,” Salisbury was quoted as saying.
As of 3 December 2009, 11.2 million doses of Pandemrix had been delivered to health services in the UK, where the vaccine formed the bulk of the government’s mass vaccination programme.
In their Patient Information Leaflet, GSK state that the following may occur:
Very common (affects more than 1 in 10 people):
Headache;
Tiredness;
Pain, redness, swelling or a hard lump at the injection site;
Fever;
Aching muscles, joint pain
Common (affects at least 1 in 100):
Warmth, itching or bruising at the injection site;
Increased sweating, shivering, flu-like symptoms;
Swollen glands in the neck, armpit or groin
Uncommon (affects at least 1 in 1,000):
Tingling or numbness of the hands or feet;
General constitutional upset of sleepiness or sleeplessness, generally feeling unwell, dizziness;
Diarrhea, vomiting, stomach pain, feeling sick;
Skin reactions of itching, rash or urticaria (hives)
Rare (affects at least 1 in 10,000):
Serious generalised allergic reactions of anaphylaxis;
Fits;
Severe stabbing or throbbing pain along one or more nerves;
Low blood platelet count which can result in bleeding or bruising
Very Rare (affects less than 1 in 10,000 people):
Vasculitis;
Neurological disorders such as encephalomyelitis, neuritis or Guillain–Barré syndrome temporary paralysis
The A-H1N1 pandemic cure: Tamiflu and Relenza
There are two main medicines that are being used in the treatment – Tamiflu (Oseltamivir), which is the main medicine being given to patients of A-H1N1 in Malta, and Relenza (zanamivir), which is given to patients that are allergic to Tamiflu.
Tamiflu (the trade name of the drug Oseltamivir) is an antiviral drug that slows the spread of influenza virus between cells in the body by stopping the virus from chemically cutting ties with its host cell.
The drug is taken orally in capsules or as a suspension. It has been used to treat and prevent Influenzavirus A and Influenzavirus B infection in over 50 million people since 1999.
Oseltamivir becomes active in the body once it passes through the liver. was the first orally active neuraminidase inhibitor commercially developed.
It was developed by C.U. Kim, W. Lew and X. Chen of US based Gilead Sciences and is currently marketed by Hoffmann–La Roche (Roche). In Japan, it is marketed by Chugai Pharmaceutical Co., which is more than 50 per cent owned by Roche.
As of December 2009, the World Health Organization (WHO) reported that 136 out of over 10,000 samples of the prevalent 2009 pandemic A-H1N1 (swine) flu tested worldwide have shown resistance to oseltamivir. This contrasts sharply with the 99.6 per cent of the seasonal A-H1N1 flu strains tested which have resistance to oseltamivir.
The Centers for Disease Control and Prevention (CDC) recommends physicians prioritize which patients they prescribe oseltamivir to. Specifically, people hospitalized with more severe illness, children younger than 2 years old, adults over 65, pregnant women, people with certain chronic medical or immunosuppressive conditions and adults under 19 on long-term aspirin therapy.
However, they also advise that children and adults presenting with suspected flu that have symptoms of lower respiratory tract illness or clinical deterioration should also receive prompt empiric antiviral therapy, regardless of previous health or age.
Common adverse drug reactions (ADRs) associated with oseltamivir therapy (occurring in over 1 per cent of clinical trial participants) include: nausea, vomiting, diarrhoea, abdominal pain, and headache.
Rare ADRs include: hepatitis and elevated liver enzymes, rash, allergic reactions including anaphylaxis, and Stevens-Johnson syndrome.
Various other ADRs have been reported in post marketing surveillance including: toxic epidermal necrolysis, cardiac arrhythmia, seizure, confusion, aggravation of diabetes, and haemorrhagic colitis.
There are concerns that oseltamivir may cause dangerous psychological, neuropsychiatric side effects including self harm in some users. These dangerous side effects occur more commonly in children than in adults. This stems from cases in Japan, where the drug is most heavily prescribed, consuming 60 per cent of the world’s production. Concern has focused on teenagers, but problems have also been reported in children and adults.
Zanamivir (sold under the trade name Relenza) is a neuraminidase inhibitor used in the treatment and prophylaxis of Influenzavirus A and Influenzavirus B.
Zanamivir was the first neuraminidase inhibitor commercially developed. It is currently marketed by GlaxoSmithKline under the trade name Relenza.
According to the Centers for Disease Control and Prevention (CDC), no flu, seasonal or pandemic, has shown any signs of resistance to zanamivir.
Zanamivir was discovered in 1989 by scientists led by Mark von Itzstein, at the Victorian College of Pharmacy, Monash University, in collaboration with the CSIRO and scientists at Glaxo, UK.
Zanamivir was the first of the neuraminidase inhibitors. The discovery was funded initially by the Australian biotechnology company Biota and was part of Biota’s ongoing program to develop antiviral agents through rational drug design.
Biota, being only a small company, was not able to bring zanamivir to market by itself. In 1990, zanamivir patent rights were licensed to Glaxo, now GlaxoSmithKline (GSK).
In 1999, the product was approved for marketing in the USA and subsequently has been registered by GSK in a total of 70 countries (GlaxoSmithKline News release, 2006).
Zanamivir is delivered via Glaxo’s proprietary Diskhaler inhalation device. The license agreement entitled Biota to receive a 7% royalty on Glaxo’s sales of zanamivir
Howver, Biota commenced legal proceedings against Glaxo for not marketing Zananvir enough once Glaxo issued Oseltamivir to the market in 1999.
Recently, the reported oseltamivir-resistance H5N1 virus neuraminidase still retaining susceptibility to zanamivir indicates that the structure of zanamivir has some advantages over oseltamivir in binding to the active pocket of H5N1 neuraminidase.
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