Influenza A (H1N1) 2009 Monovalent Vaccine Inactivated

Class: Vaccines
VA Class: IM100

Introduction

Inactivated virus vaccine.^{97 98 99} Influenza A (H1N1) 2009 monovalent vaccine inactivated contains noninfectious, suitably inactivated 2009 influenza type A (H1N1) virus and is used to stimulate active immunity to the influenza virus strain contained in the vaccine.^{97 98 99}

Uses for Influenza A (H1N1) 2009 Monovalent Vaccine Inactivated

Prevention of 2009 Influenza A (H1N1) Virus Infection

Prevention of 2009 pandemic influenza A (H1N1) virus infection in adults,^{97 98 99} adolescents,^{97 98} and children ≥6 months of age.⁹⁷

Influenza outbreaks caused by the 2009 influenza A (H1N1) virus, previously referred to as the novel 2009 influenza A (H1N1) virus or swine-origin influenza A (H1N1) virus, were initially reported in several countries, including the US, beginning in March and April 2009.^{100 508 513 514 515 516 517 532} On June 11, 2009, the WHO declared that the first global influenza pandemic in 41 years was occurring and issued a phase 6 pandemic alert regarding 2009 influenza A (H1N1).^{513 529} A phase 6 pandemic is characterized by human-to-human transmission of an animal or human-animal reassortant virus and sustained community level outbreaks of the virus in 2 or more countries in a single WHO region and sustained community level outbreaks in at least one other country in a different WHO region.⁵²¹

Influenza viruses can cause seasonal epidemics and, occasionally, global pandemics (an epidemic that affects the whole population).^{100 437 521} Prior to 2009, the 3 most recent influenza pandemics were the 1918 Spanish flu pandemic (caused 20–50 million deaths worldwide including about 500,000 deaths in the US), the 1957 Asian flu pandemic (caused 1–4 million deaths worldwide including about 70,000 deaths in the US), and the 1968 Hong Kong flu pandemic (1–4 million deaths worldwide including about 34,000 deaths in the US).^{437 521}

The 2009 influenza A (H1N1) virus appears to be a triple-reassortant swine influenza virus containing genes from human, swine, and avian influenza A viruses.^{517 522 532} The virus contains a unique combination of gene segments not previously reported among human or swine influenza A in the US or elsewhere.^{514 517 522 532} The virus, however, may be antigenically similar to classical swine influenza A (H1N1) viruses and triple reassortant swine influenza A (H1N1) viruses that circulate in pigs and have been associated with sporadic human infections.^{522 532}

The 2009 influenza A (H1N1) virus is antigenically and genetically distinct from circulating seasonal human influenza A (H1N1) viruses, and preliminary studies indicate that a majority of the population may be susceptible to the virus.^{508 522} This virus is expected to continue to circulate worldwide, including in the US, during the 2009–2010 influenza season in addition to strains of seasonal influenza A and B.^{100 465 508 512 513 526}

Vaccination using an appropriate vaccine is the most effective strategy for preventing influenza and its complications.^{100 508}

Seasonal influenza virus vaccines used for prevention of seasonal influenza are reformulated each year to contain antigens representative of the strains of influenza A and B viruses likely to circulate in the US during the upcoming influenza season.^{100 510 511} Seasonal influenza vaccines for the 2009–2010 influenza season are not expected to provide protection against 2009 influenza A (H1N1) virus infection.^{100 508}

For prevention of 2009 influenza A (H1N1) virus infection, 2 different types of monovalent influenza vaccine are commercially available in the US: parenteral vaccine containing inactivated virus^{97 98 99} and intranasal vaccine containing live, attenuated virus.⁵²³ Both vaccine types are produced using an A/California/7/2009 (H1N1)v-like strain.^{97 98 99 508 523} (See Actions.)

Initial FDA approval of each of the commercially available inactivated influenza A (H1N1) 2009 monovalent vaccines was based on safety and efficacy data for the seasonal inactivated trivalent influenza vaccine produced by the same manufacturer (Afluria, manufactured by CSL; Fluvirin, manufactured by Novartis; Fluzone, manufactured by Sanofi Pasteur) and was considered a strain change to each manufacturer's FDA-approved seasonal inactivated influenza vaccine.^{97 98 99 528} Studies are ongoing to evaluate safety and efficacy of monovalent influenza A (H1N1) 2009 vaccines.^{97 98 508 524 528}

Although influenza vaccination using an appropriate vaccine is the most effective method for preventing influenza and influenza-related complications,^{100 508} there may be some situations, including during influenza pandemics, when use of antiviral agents may be indicated for prevention or treatment of influenza.^{100 437 465 512 513 520 521} CDC has issued updated interim recommendations concerning the use of antiviral agents for prevention and treatment of influenza, including 2009 influenza A (H1N1) and seasonal influenza.⁵¹² The CDC recommendations are available at and should be used to guide selection of the most appropriate antivirals for prevention and treatment of influenza and to prioritize use of such agents in patients at higher risk for influenza-related complications.⁵¹²

Because initial supplies of influenza A (H1N1) 2009 vaccine may not be sufficient to meet demands for the vaccine, the USPHS Advisory Committee on Immunization Practices (ACIP) identified initial target groups for priority vaccination.⁵⁰⁸ These individuals are at higher risk for influenza or influenza-related complications, are likely to come in contact with influenza viruses as part of their occupation and could transmit the viruses to others in medical care settings, or are close contacts of infants too young to be vaccinated (<6 months of age).⁵⁰⁸ (See table.) As supplies of the vaccine increase and demand for vaccine among individuals in initial priority target groups is met, CDC or ACIP is likely to revise recommendations to include additional target groups (e.g., all individuals 25 through 64 years of age, adults ≥65 years of age).^{508 533}

ACIP Recommendations for Priority Vaccination Against 2009 Pandemic Influenza A (H1N1) Virus:508

Initial Target Groups for Vaccine Supplies

Pregnant women

Individuals who live with or provide care for infants <6 months of age (e.g., parents, siblings, day-care providers)

Health-care and emergency medical services personnel

Individuals 6 months through 24 years of age

Adults 25 through 64 years of age with medical conditions that put them at higher risk for influenza-related complications, including chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, cognitive, neurologic/neuromuscular, hematologic, or metabolic (including diabetes mellitus) disorders

Adults 25 through 64 years of age who are immunosuppressed, including those receiving immunosuppressive drugs and those with HIV infection

Subset of Initial Target Groups for Priority Vaccination if Vaccine Supplies are Limited

Pregnant women

Individuals who live with or provide care for infants <6 months of age (e.g., parents, siblings, day-care providers)

Health-care and emergency medical services personnel who have direct contact with patients or infectious materials

Children 6 months through 4 years of age

Children and adolescents 5–18 years of age who have medical conditions that put them at higher risk for influenza complications, including chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, cognitive, neurologic/neuromuscular, hematologic, or metabolic (including diabetes mellitus) disorders

Based on current prescribing information, parenteral inactivated influenza A (H1N1) 2009 vaccine can be used for prevention of 2009 influenza A (H1N1) virus infection in any of the target groups identified for priority vaccination, unless contraindicated.^{97 98 99} Based on current prescribing information, the intranasal live influenza A (H1N1) 2009 vaccine may be used in some (but not all) of the target groups.⁵²³

Information regarding influenza surveillance and updated recommendations for prevention and treatment of 2009 influenza A (H1N1) virus infection is available at . CDC information on treatment and prevention of seasonal influenza is available at .

Influenza A (H1N1) 2009 Monovalent Vaccine Inactivated Dosage and Administration

Administration

IM Administration

Administer by IM injection.^{97 98 99}

Shake vaccine vial before withdrawing a dose.^{97 98 99} Shake prefilled syringe immediately before administering a dose.^{97 98 99} Discard vaccine if it contains particulates, appears discolored, or cannot be resuspended with thorough agitation.^{97 98 99}

Do not mix with any other vaccine or solution.^{97 98 99}

To ensure delivery into muscle, IM injections should be made at a 90° angle to the skin using a needle length appropriate for the individual's age and body mass.⁴⁷⁵ For adults and adolescents, administer IM into the deltoid muscle.^{97 98 99 475} In children ≥3 years of age, IM injections should be made into the deltoid muscle if muscle mass is adequate; alternatively, the anterolateral thigh can be used.^{97 98 475} In children 6 months to 2 years of age, IM injections should preferably be made in the anterolateral aspect of the thigh.^{97 475}

Do not administer into buttock muscle because of potential for injection-associated injury to sciatic nerve.^{97 98 475} Do not administer into any area where there may be a major nerve trunk.^{97 98}

ACIP states that aspiration (i.e., pulling back on the syringe plunger after needle insertion and before injection) is not required because large blood vessels are not present at recommended IM injection sites.⁴⁷⁵

Since syncope may occur following vaccination, observe vaccinees for approximately 15 minutes after the dose.^{112 475} Syncope occurs most frequently in adolescents and young adults,^{112 475} and may be averted if vaccinees sit or lie down for 15 minutes after vaccination.¹¹² If syncope occurs, observe patient until symptoms resolve.^{112 475}

May be administered simultaneously with other age-appropriate vaccines.⁵³³ If given at the same time as other parenteral vaccines during a single health-care visit, each vaccine should be given with a different syringe and at different injection sites.⁹⁷ (See Other Vaccines under Interactions.)

ACIP has identified specific target groups who should receive influenza A (H1N1) 2009 vaccine beginning as soon as initial supplies become available in October, unless contraindicated.⁵⁰⁸ These individuals are at higher risk for influenza or influenza-related complications, are likely to come in contact with influenza viruses as part of their occupation and could transmit influenza viruses to others in medical care settings, or are close contacts of infants too young to be vaccinated (<6 months of age).⁵⁰⁸ (See Uses.)

Dosage

Clinical studies are ongoing to determine the optimal dosage, number of doses, and vaccination schedule for parenteral inactivated influenza A (H1N1) 2009 monovalent vaccine.^{97 98 99 508 528} The following dosages are based on available data to date.^{97 98}

A single-dose regimen is recommended for adults and children ≥10 years of age.^{97 98 99} A 2-dose regimen is recommended for children 6 months through 9 years of age.^{97 98}

Influenza A (H1N1) 2009 vaccine inactivated manufactured by CSL is used only in adults ≥18 years of age.⁹⁹

Influenza A (H1N1) 2009 vaccine inactivated manufactured by Sanofi Pasteur may be used in adults, adolescents, and children ≥6 months of age.⁹⁷

Influenza A (H1N1) 2009 vaccine inactivated manufactured by Novartis may be used in adults, adolescents, and children ≥4 years of age.⁹⁸

Pediatric Patients

Prevention of 2009 Influenza A (H1N1) Virus Infection

Children and Adolescents 6 Months through 17 Years of Age (Influenza A (H1N1) 2009 Vaccine Inactivated Manufactured by Sanofi Pasteur)

IM

Children 6 through 35 months of age: Two 0.25-mL doses administered approximately 1 month apart.⁹⁷

Children 36 months through 9 years of age: Two 0.5-mL doses administered approximately 1 month apart.⁹⁷

Children and adolescents 10 through 17 years of age: Single 0.5-mL dose.⁹⁷

Children and Adolescents 4 through 17 Years of Age (Influenza A (H1N1) 2009 Vaccine Inactivated Manufactured by Novartis)

IM

Children 4 through 9 years of age: Two 0.5-mL doses administered approximately 1 month apart.⁹⁸

Children and adolescents 10 through 17 years of age: Single 0.5-mL dose.⁹⁸

Adults

Prevention of 2009 Influenza A (H1N1)Virus Infection

Adults 18 Years of Age or Older

IM

Single 0.5-mL dose.^{97 98 99}

Special Populations

Hepatic Impairment

No specific dosage recommendations.^{97 98 99}

Renal Impairment

No specific dosage recommendations.^{97 98 99}

Geriatric Patients

No specific dosage recommendations.^{97 98 99} (See Geriatric Use under Cautions.)

Cautions for Influenza A (H1N1) 2009 Monovalent Vaccine Inactivated

Contraindications

• 
  

  Hypersensitivity to eggs,^{98 99} egg protein,^{97 98} chicken protein,⁹⁹ or any vaccine component.^{97 98} (See Sensitivity Reactions under Cautions.)

  
  


• 
  

  Life-threatening reaction to previous dose of any influenza vaccine.^{97 98 99}

  
  


• 
  

  Influenza A (H1N1) 2009 vaccine inactivated manufactured by CSL: Hypersensitivity to neomycin or polymyxin.⁹⁹ (See Neomycin and/or Polymyxin B Allergy under Cautions.)

  
  

Warnings/Precautions

Sensitivity Reactions

Hypersensitivity Reactions

Studies using seasonal parenteral inactivated influenza vaccine indicate rare reports of immediate, presumably allergic reactions (e.g., urticaria, angioedema, anaphylaxis, allergic asthma).^{97 98 99 103 143 441 463 473} Reactions may result from sensitivity to some vaccine component, including residual egg protein.^{97 98 99 103 143 441 463 473}

Parenteral inactivated influenza A (H1N1) 2009 vaccine is produced using embryonated chicken eggs (the same process used for manufacture of seasonal parenteral inactivated influenza vaccine) and can contain residual egg protein that may induce immediate hypersensitivity reactions, including anaphylaxis, in individuals with severe egg allergy.^{97 98 99} CDC and ACIP state that asking patients if they can eat eggs without adverse effects is a reasonable way to identify those who may be at risk for allergic reactions if they receive the vaccine.^{475 533} Those who are able to eat eggs or egg products safely usually can receive vaccines produced using chicken eggs; those with a history of anaphylactic or other immediate hypersensitivity reaction (e.g., hives, angioedema, allergic asthma) to eggs or egg proteins should not receive such vaccines.⁴⁷⁵ (See Contraindications under Cautions.)

Prior to administration, review patient’s history with respect to possible hypersensitivity to vaccine components, including egg and egg products.⁹⁸ Epinephrine and other appropriate agents should be readily available in case anaphylaxis occurs.^{97 98 99}

Do not administer additional vaccine doses to any individual who experienced life-threatening reactions to a previous dose.^{97 98 99} (See Contraindications under Cautions.)

Neomycin and/or Polymyxin B Allergy

Influenza A (H1N1) 2009 vaccine inactivated manufactured by CSL: Contains trace amounts of neomycin sulfate (≤0.2 picograms) and polymyxin B (≤0.03 picograms).⁹⁹ Manufacturer states the vaccine is contraindicated in individuals hypersensitive to neomycin or polymyxin.⁹⁹

Influenza A (H1N1) 2009 vaccine inactivated manufactured by Novartis: Contains neomycin sulfate (≤2.5 mcg) and polymyxin B (≤3.75 mcg).⁹⁸

Neomycin allergy usually results in delayed-type (cell-mediated) hypersensitivity reactions manifested as contact dermatitis.⁴⁷⁵ ACIP and AAP state that vaccines containing trace amounts of neomycin should not be used in individuals with a history of anaphylactic reaction to neomycin, but may be considered in those with a history of delayed-type neomycin hypersensitivity if benefits of vaccination outweigh risks.^{112 475}

Thimerosal Allergy

All multiple-dose vials of influenza A (H1N1) 2009 vaccine inactivated contain thimerosal as a preservative;^{97 98 99} some preparations of the vaccine in prefilled syringes are preservative-free but contain trace amounts of thimerosal from the manufacturing process.⁹⁸ (See Thimerosal Precautions under Cautions.) Hypersensitivity reactions to thimerosal contained in vaccines have been reported in some individuals.^{100 140 427 498 500} These reactions usually manifest as local, delayed-type hypersensitivity reactions (e.g., erythema, swelling),^{100 140 427 475} but a generalized reaction manifested as pruritus and an erythematous, maculopapular rash on all 4 extremities has been reported rarely.⁵⁰⁰ Even when patch or intradermal tests for thimerosal sensitivity are positive, most individuals do not develop hypersensitivity reactions to thimerosal administered as a component of vaccines.^{100 140 475}

ACIP states that a history of delayed-type hypersensitivity to thimerosal is not a contraindication to use of vaccines that contain thimerosal.⁴⁷⁵

Ongoing Safety Review

Safety and adverse effects reported with parenteral inactivated influenza A (H1N1) 2009 vaccine are expected to be similar to those reported for seasonal parenteral inactivated influenza vaccines (e.g., mild fever, body aches, fatigue, soreness at injection site).⁵²⁸ However, as with any medical product, serious adverse events may occur.⁵²⁸

FDA and CDC are closely monitoring safety of influenza A (H1N1) 2009 vaccines through a collaborative effort between CDC, US Department of Health and Human Services (HHS), and other government agencies.⁵²⁸ Only limited data are available to date regarding adverse effects reported with influenza A (H1N1) 2009 vaccine.⁵²⁴ (See Common Adverse Effects.)

Guillain-Barré Syndrome

In 1976, a temporal association was noted between administration of A/New Jersey/76 (swine) influenza vaccine and Guillain-Barré syndrome (GBS, polyradiculoneuritis).^{97 98 99 100 278 279 364 365} The annual incidence of GBS is 10–20 cases per million in adults; the increased risk of GBS in individuals who received A/New Jersey/76 (swine) influenza vaccine was estimated to be 1 additional case of GBS per 100,000 vaccinees.^{100 192 275 276 277 278 279} Epidemiologic evidence indicates that the associated risk between administration of the A/New Jersey/76 (swine) influenza vaccine and GBS did not extend beyond 6 weeks after vaccination,¹⁹¹ and vaccinees who received the 1976 swine influenza vaccine have not been shown to exhibit an increased risk of GBS with subsequent vaccine formulations.²⁸⁰

Evidence for an increased risk of developing GBS with subsequent influenza vaccine formulations prepared from other virus strains is unclear;^{97 98 99 100 192 275 276 277 280} however, it is difficult to estimate precisely the risk for a condition as rare as GBS.^{100 192 275 276 277 280}

If influenza vaccine does pose a risk, the estimated risk for GBS probably is slightly more than 1 additional case per million vaccinees.^{97 98 99 100 152 364 365} ACIP states that there is no evidence that the case-fatality ratio for GBS differs among vaccinated and unvaccinated individuals.¹⁰⁰

Carefully consider possible benefits and potential risks of influenza A (H1N1) 2009 vaccine in individuals who experienced GBS within 6 weeks of previous influenza vaccination.^{97 98 99 441 463}

AAP states that influenza vaccines should not be used in children who developed GBS within 6 weeks after a dose of any influenza vaccine.⁴⁶⁵ ACIP states that benefits of influenza vaccine may outweigh risks in individuals with a history of GBS who are at high risk for severe influenza-related complications.¹⁰⁰ However, it may be prudent to avoid influenza vaccine in individuals who are not at high risk for severe influenza complications if they experienced GBS within 6 weeks after previous influenza vaccination.¹⁰⁰

Other Neurologic Effects

Neurologic disorders (not defined as GBS) have been temporally associated with seasonal inactivated influenza vaccine, including encephalopathy,^{97 98 99 103 143 441 463 473} encephalomyelitis,⁴⁴¹ neuralgia,^{99 143 473} optic neuritis/neuropathy,^{97 98 99 103 143 441 463 473} partial facial paralysis,^{97 98 99 103 143 441 463 473} Bell's palsy,^{97 98 103 143} neuritis or neuropathy,^{98 99 143 473} paresthesia,^{99 103 143 463 473} hypoesthesia,⁴⁶³ and brachial plexus neuropathy.^{97 98 99 103 143 203 204 205 206 207 208 441 463 473} Seizures^{97 98 103 143 463 473} and myelitis (including encephalomyelitis and transverse myelitis)^{97 98 99 103 143 473 358} also reported rarely with seasonal inactivated influenza vaccine.

Individuals with Altered Immunocompetence

May be administered to individuals immunosuppressed as the result of disease or immunosuppressive therapy.⁵⁰⁸ Immunocompromised individuals may be at increased risk of severe infections and should be vaccinated against influenza A (H1N1) infection.⁵⁰⁸ Consider possibility that immune response to the vaccine may be reduced in these individuals.^{97 98 99}

In recommendations regarding seasonal influenza, CDC, National Institutes of Health (NIH), IDSA, AAP, and other experts state that HIV-infected children, adolescents, and adults should be vaccinated against influenza; however, parenteral inactivated influenza vaccine (not intranasal live vaccine) should be used in HIV-infected individuals.^{378 509} Studies using seasonal influenza virus vaccine inactivated indicate antibody response may be inversely correlated with severity of the disease.^{100 101 106 109 110 112 116 232 233 255 260 310 375 376 428} Although seasonal parenteral inactivated influenza vaccine has been highly effective in preventing symptomatic, laboratory-confirmed influenza infection in HIV-infected individuals with mean CD4⁺ T-cell counts of 400/mm³, the vaccine may be less effective in those with more advanced disease and lower CD4⁺ T-cell counts (e.g., <100/mm³).¹⁰⁰ A second dose of seasonal influenza vaccine does not appear to improve immune response in these individuals.¹⁰⁰

Individuals with a History of Influenza

May be administered to individuals who have had an influenza-like illness.^{531 533} The vaccine is not harmful in individuals who previously had diagnosed or undiagnosed influenza illness, including 2009 influenza A (H1N1) infection,^{531 533} and is not harmful in individuals who already have some existing immunity to the 2009 influenza A (H1N1) virus.⁵³³

If influenza A (H1N1) 2009 vaccine is indicated (see Uses), CDC recommends that the vaccine be administered even in individuals who have had an influenza-like illness previously, unless such individuals had a confirmed diagnosis of 2009 influenza A (H1N1) infection based on results of a real-time reverse transcriptase-polymerase chain reaction (RT-PCR) test for 2009 influenza A (H1N1) virus.^{531 533} Individuals who had an influenza-like illness and were tested using a less specific test (e.g., rapid antigen detection assay) should not assume they had 2009 influenza A (H1N1) infection, even if they became ill after being exposed to an individual with confirmed 2009 influenza A (H1N1) infection.⁵³³

Thimerosal Precautions

Although it was suggested that thimerosal in vaccines theoretically could have adverse effects in vaccine recipients, there is no conclusive evidence that the low levels of thimerosal contained in vaccines cause harm in vaccine recipients.^{100 475 492 493 494 499 501 502 503 504 505 506} A link between thimerosal in vaccines and neurodevelopmental disorders in children (autism, attention deficit/hyperactivity disorder [AHDH], speech or language delay) possibly related to mercury neurotoxicity has been theorized; however, considerable evidence has accumulated that supports the absence of substantial risk for neurodevelopmental disorders or other harm resulting from exposure to thimerosal-containing vaccines.^{100 493 494 499 501 502 503 504 505 506} In 2004, the Immunization Safety Review Committee of the Institute of Medicine (IOM) examined the hypothesis that thimerosal-containing vaccines are causally associated with autism and concluded that the body of epidemiologic evidence favors rejection of a causal relationship between these vaccines and autism.⁵⁰⁶

Analysis of adverse effects reported to the Vaccine Adverse Event Reporting System (VAERS) indicates that there is no difference in the incidence of injection site reactions, rash, or infections in infants 6–23 months of age who received preservative-containing (thimerosal-containing) seasonal inactivated influenza vaccine compared with those who received preservative-free preparations of the vaccine.^{100 497} To date, the only adverse effects known to be caused by thimerosal contained in vaccines are hypersensitivity reactions.^{100 140 427 475 493} (See Thimerosal Allergy under Cautions.)

USPHS, ACIP, AAP, American Association of Family Physicians (AAFP), and other experts state that use of vaccines that contain thimerosal is preferable to withholding vaccination since failure to provide protection against vaccine-preventable diseases may represent an immediate threat, especially in infants.^{100 401 402 403 465} ACIP states that benefits of influenza vaccination for all recommended groups (including pregnant women and young children) outweigh concerns related to theoretical risks of thimerosal exposure from vaccination with preparations containing thimerosal.¹⁰⁰ AAP states that the benefits of protecting children (including children at high risk with underlying CNS disorders) outweigh the hypothetical risks associated with the minute amounts of thimerosal contained in some currently available influenza vaccine preparations.⁴⁶⁵

Influenza A (H1N1) 2009 vaccine inactivated manufactured by CSL: Commercially available in 0.5-mL prefilled syringes as a preservative-free formulation (thimerosal not used in manufacturing process).⁹⁹ Also available in multiple-dose vials containing thimerosal as a preservative (24.5 mcg of mercury per 0.5-mL dose).⁹⁹

Influenza A (H1N1) 2009 vaccine inactivated manufactured by Novartis: Commercially available in prefilled syringes in a preservative-free formulation containing only trace amounts of thimerosal from the manufacturing process (≤1 mcg of mercury per 0.5 mL).⁹⁸ Also available in multiple-dose vials containing thimerosal as a preservative (25 mcg of mercury per 0.5-mL dose).⁹⁸

Influenza A (H1N1) 2009 vaccine inactivated manufactured by Sanofi Pasteur: Commercially available in 0.25- and 0.5-mL prefilled syringes and single-dose 0.5-mL vials as a preservative-free formulation (thimerosal not used in manufacturing process).⁹⁷ Also available in multiple-dose vials containing thimerosal as a preservative (25 mcg of mercury per 0.5-mL dose).⁹⁷

Limitations of Vaccine Effectiveness

Studies using seasonal influenza vaccines indicate up to 2 weeks may be required for protection to develop following influenza vaccination.¹⁰⁰ Preliminary studies using parenteral inactivated influenza A (H1N1) 2009 vaccine indicate an immune response can occur as early as 8–10 days after vaccination.⁵³⁰

May not protect all vaccine recipients against 2009 influenza A (H1N1) virus infection.^{97 98 99}

Does not provide protection against seasonal influenza A and B viruses;⁵⁰⁸ seasonal influenza vaccine for the 2009–2010 influenza season is indicated to provide protection against seasonal influenza.^{100 508 531}

Duration of Immunity

Studies using seasonal influenza vaccines indicate that immunity declines during the year after influenza vaccination.^{100 488} Data are not available to date regarding the duration of protection following vaccination with parenteral inactivated influenza A (H1N1) 2009 vaccine.

Concomitant Illness

Vaccination generally should be delayed in individuals with moderate to severe acute febrile illness until symptoms have subsided.^{100 475} ACIP states that minor acute illness (with or without fever), generally does not preclude vaccination.^{100 475}

Individuals with Bleeding Disorders

ACIP states that vaccines may be given IM to individuals who have bleeding disorders or are receiving anticoagulant therapy if a clinician familiar with the patient's bleeding risk determines that the preparation can be administered with reasonable safety.⁴⁷⁵ In these cases, use a fine needle (23 gauge) to administer the vaccine and apply firm pressure to the injection site (without rubbing) for ≥2 minutes.⁴⁷⁵ If patient is receiving antihemophilia therapy, administer the IM vaccine shortly after a scheduled dose of such therapy.⁴⁷⁵

Advise individual and/or their family about the risk of hematoma from IM injections.⁴⁷⁵

Improper Storage and Handling

Improper storage or handling of vaccines may result in loss of vaccine potency and reduced immune response in vaccinees.⁴⁷⁵

Inspect all vaccines upon delivery and monitor during storage to ensure that the appropriate temperature is maintained.^{99 475 476}

Do not administer vaccine that has been mishandled or has not been stored at the recommended temperature.^{99 475} (See Storage under Stability.) If there are concerns about mishandling, contact the manufacturer or state or local health departments for guidance on whether the vaccine is usable.^{475 476}

Specific Populations

Pregnancy

Category C.^{97 98 99}

Manufacturers state that parenteral inactivated influenza A (H1N1) 2009 vaccine should be used in pregnant women only when clearly needed.^{97 98 99}

CDC, ACIP, American College of Obstetricians and Gynecologists (ACOG), American College of Physicians (ACP), NIH, IDSA, and other experts state that parenteral inactivated influenza vaccine (not intranasal live influenza vaccine) should be used for prevention of seasonal influenza in pregnant women.^{100 378 479 531}

Because pregnant women are at risk for influenza complications, CDC and ACIP recommend that pregnant women receive priority vaccination against 2009 influenza A (H1N1) virus infection, unless contraindicated.^{508 531} (See Uses.)

ACIP states that benefits of influenza vaccination for pregnant women outweigh theoretical risks from thimerosal exposure by vaccination with preparations containing thimerosal;¹⁰⁰ CDC states that pregnant women may receive influenza A (H1N1) 2009 vaccine with or without thimerosal.⁵³¹ (See Thimerosal Precautions under Cautions.)

Lactation

Safety and efficacy not established in breastfeeding mothers.^{97 98 99}

Not known whether parenteral inactivated influenza A (H1N1) vaccine is distributed into milk.^{97 98 99} Manufacturers recommend caution.^{97 98 99}

Inactivated vaccines do not affect safety of breastfeeding for lactating women or their infants.⁴⁷⁵ ACIP and CDC state that breastfeeding does not adversely affect immune response and is not a contraindication to vaccination.^{100 117 475}

Pediatric Use

Influenza A (H1N1) 2009 vaccine inactivated manufactured by CSL: Safety and efficacy not established in children <18 years of age.⁹⁹

Influenza A (H1N1) 2009 vaccine inactivated manufactured by Novartis: Safety and efficacy not established in children <4 years of age.⁹⁸

Influenza A (H1N1) 2009 vaccine inactivated manufactured by Sanofi Pasteur: Safety and efficacy not established in infants <6 months of age.⁹⁷

ACIP states t