Options for 20012002 Influenza Vaccine Composition

1
Options for 2001-2002 Influenza Vaccine
Composition

• Summary of Data
• Options with Pros and Cons

2
Influenza A(H1N1) Viruses

• Little antigenic heterogeneity observed
• HA of most strains antigenically similar to A/New
  Caledonia/99 vaccine strain
• The NA genes of current strains are similar to
  the vaccine strain
• Low reactors dont fall into one genetic group
• H1N1 viruses are generally well inhibited by
  ferret and human antiserum vs. A/New Caledonia
• Current vaccine strain in vaccine for 1 year

3
H1N1 Option 1 Maintain Current Vaccine Strain

• Pros
• Current vaccine strain is immunogenic and well
  matched to currently circulating viruses
• Manufacturing is well-defined and predictable
• No new vaccine candidates are available
• Con
• A variant strain could be identified in the next
  2-3 weeks

4
H1N1 Option 2 Update Current Vaccine Strain

• Pro
• Might provide closer genetic match to next years
  viruses if correct sub lineage is chosen
• Cons
• No clear advantage based on antigenic
  characterization or serologic results
• No superior alternate vaccine candidate

5
H1N1 Option 3. Defer to Accumulate Additional Data

• Pro
• More data will be available in the next 2-3 weeks
  (including analyses of new Chinese H1N1 viruses)
• Con
• Additional data may not alter the current
  considerations since global data consistently
  indicate a good vaccine match

6
Summary for Influenza A(H1N1) Viruses

• Although influenza activity associated with H1N1
  viruses has been low worldwide in recent years,
  significant H1N1 activity has occurred this
  season.
• The majority of current viruses are antigenically
  similar to the A/New Caledonia/99 vaccine strain,
  however, viruses similar to the A/Johannesburg/96
  reference strain were also identified.
• Human serologic responses suggest that the
  current vaccine strain is immunogenic and
  provides a good antibody response against current
  viruses from both antigenic/genetic groups.

7
Influenza A(H3N2) Viruses

• Little antigenic heterogeneity observed
• HA of most strains antigenically similar to
  A/Panama/99 vaccine strain
• The NA genes of many current strains fall into a
  different genetic group from A/Panama/99
• Low reactors (few) do not fall into any
  particular genetic group
• H3N2 viruses are generally well inhibited by
  ferret and human antiserum vs. A/Panama/99
• Current vaccine strain in vaccine for 1 year

8
H3N2 Option 1 Maintain Current Vaccine Strain

• Pros
• Current vaccine strain is immunogenic and well
  matched to currently circulating viruses
• Manufacturing is well-defined and predictable
• No obvious new vaccine candidate
• Con
• A new variant might be identified in the next 2-3
  weeks

9
H3N2 Option 2 Update Current Vaccine Strain

• Pro
• May provide closer genetic match to HA and
  especially to NA of next years viruses
• Cons
• No clear advantage based on antigenic
  characterization or serologic results
• No clear alternate vaccine candidate

10
H3N2 Option 3 Defer to Accumulate Additional Data

• Pros
• Since H3N2 viruses cause most serious morbidity
  and mortality, choice should be made carefully
• A few additional pieces of data will be available
  in the next 2-3 weeks
• Con
• Additional data may be insufficient to alter
  current considerations

11
Summary for Influenza A(H3N2) Viruses

• In contrast to most recent years, few H3N2
  viruses have been isolated globally.
• Current viruses are antigenically similar to the
  A/Panama/99 vaccine strain.
• Serologic responses suggest that the current
  vaccine strain is immunogenic and provides an
  equivalent antibody response against most current
  viruses.

12
Influenza B Viruses

• Antigenic drift has been detected
• A new variant represented by B/Sichuan/379/99 has
  been identified as a prototype variant strain
• The NA genes of many current strains are
  generally similar to vaccine strain
• No evidence for circulation of B/Vic-lineage
  strains
• B viruses are generally less well inhibited by
  ferret and human antiserum vs. B/Yamanashi/98
• Current vaccine strain in vaccine for 2 years

13
Influenza B Option 1 Maintain Current Vaccine
Strain

• Pros
• Current vaccine strain is immunogenic
• Manufacturing is well defined and predictable
• Cons
• Current influenza B strains are not well
  inhibited by ferret serum to vaccine strain
• Human serologic responses vs. recent strains
  reduced
• Egg isolates with appropriate antigenic
  properties are being evaluated as candidate
  vaccine strains

14
Influenza B Option 2 Update Current Vaccine
Strain

• Pros
• Provide a better antigenic match with current B
  strains
• Vaccine candidate strains (e.g., B/JHB/5/99 and
  B/Vic/504/2000) were used to manufacture vaccines
  for the Southern Hemisphere
• Cons
• No data available on immunogenicity of vaccines
  produced with recent strains
• Many recent influenza B egg isolates grow poorly

15
Influenza B Option 3 Defer to Accumulate
Additional Data

• Pros
• More data will be available in the next 2-3
  weeks, including analyses of new Chinese
  influenza B viruses
• More data are likely to be available on growth
  properties of potential vaccine candidates
• Cons
• Additional data may not alter current
  considerations

16
Summary for Influenza B Viruses

• Antigenic drift from the vaccine strain,
  B/Yamanashi/98, is apparent among current
  influenza B viruses which are antigenically and
  genetically similar to the prototype reference
  strain, B/Sichuan/379/99.
• Serologic responses suggest that the current
  vaccine strain is immunogenic but may provide a
  more limited response against current B viruses.
• A great deal of work has been done to develop
  alternate vaccine candidates.