Third wave of h1n1 flu pandemic doubtful

Third wave of h1n1 flu pandemic doubtful

Seroproection rates (antibody levels) of H1N1 have been analyzed and Canadian scientists say that a third wave of the H1N1 (swine flu) is highly improbable for 2010. Their research can be viewed in the latest issue of CMAJ (Canadian Medical Association Journal). The scientists stress, though, that individuals aged 50 or over, especially people with chronic conditions and diseases should make sure they are vaccinated.

The authors, from the BC Centre for Disease Control, University of British Columbia and BC Biomedical Laboratories, carried out a study involving 1,1127 individuals from British Columbia's Lower Mainland comparing antibody blood levels against H1N1 influenza prior to the 2009 pandemic as well as after it.

They found that:

  • Before the pandemic 10% all people under 70 years of age had levels of H1N1 antibodies deemed as protective
  • 77% of individuals over 80 years of age had H1N1 antibody protective levels before the pandemic
  • After the pandemic, in the autumn (fall) of 2009, 70% of people under 20, 44% of those aged between 20 and 49, and 30% of those aged between 50 and 79 had levels of H1N1 antibodies deemed as protective. Only 21% of those aged 70 to 79 years had adequate protection levels. Higher rates were identified among people aged at least 80 years.
The authors wrote:

The higher percentage with seroprotection we observed in the young may have resulted from higher pandemic H1N1 infection rates and earlier prioritization of pandemic H1N1 vaccine to young children.

In order to prevent a serious epidemic in a population, community-level protection needs to be above 40%, the scientists explain, especially if kids of school age are protected. School age children are major contributors to an epidemic.

The current seroprotection rate is 70% among schoolchildren and 46% overall (in the community in general).

Referring to current schoolchildren and overall seroprotection rates, the authors write:

..these findings reassure against the likelihood of a substantial third pandemic H1N1 wave during the 2010-11 season, unless there is a significant waning of antibody or change in the virus.

Immunization needs to focus on older people.

The researchers add:

Adults 50-79 years exhibited the lowest seroprotection and also remain at higher risk of severe outcomes if infected. Our findings support a shift from the prioritized immunization of the young that occurred in fall 2009 to prioritized immunization of older adults for the coming 2010-11 influenza season to protect against severe outcomes due to both pandemic and seasonal influenza.

"Prevalence of seroprotection against the pandemic (H1N1) virus after the 2009 pandemic"

Danuta M. Skowronski, Travis S. Hottes, Naveed Z. Janjua, Dale Purych, Suzana Sabaiduc, Tracy Chan, Gaston De Serres, Jennifer Gardy, Janet E. McElhaney, David M. Patrick, Martin Petric

Published online ahead of print October 18, 2010

CMAJ 10.1503/cmaj.100910

Third wave of H1N1 virus possible (Video Medical And Professional 2020).

Section Issues On Medicine: Disease