Not unexpectedly, we have seen that homologous genes have characteristic equations where the coefficients of the describing polynomials are quite close. Assuming that the DNA fidelity processes fit to this scheme of preferential arrangement of bases in conserved segments, our observations raise the possibility that DNA fragments, introduced into such segments by processes such as transpositions, that do not conform to the overall fit may be preferentially excised by the replication machinery to retain the integrity of the host sequence. If our observations here in gene sequences are extendible further to genomic sequences then it would imply that not all genetic modifications would be sustainable. Willingness of Hong Kong healthcare workers to accept pre-pandemic influenza vaccination at different WHO alert levels: two questionnaire surveys Objective To assess the acceptability of pre-pandemic influenza vaccination among healthcare workers in public hospitals in Hong Kong and the effect of escalation in the World Health Organization’s alert level for an influenza pandemic. Design Repeated cross sectional studies using self administered, anonymous questionnaires Setting Surveys at 31 hospital departments of internal medicine, paediatrics, and emergency medicine under the Hong Kong Hospital Authority from January to March 2009 and in May 2009 Participants 2255 healthcare workers completed the questionnaires in the two studies. They were doctors, nurses, or allied health professionals working in the public hospital system. Main outcome measures Stated willingness to accept pre-pandemic influenza vaccination (influenza A subtypes H5N1 or H1N1) and its associating factors. Results The overall willingness to accept pre-pandemic H5N1 vaccine was only 28.4% in the first survey, conducted at WHO influenza pandemic alert phase 3. No significant changes in the level of willingness to accept pre-pandemic H5N1 vaccine were observed despite the escalation to alert phase 5. The willingness to accept pre-pandemic H1N1 vaccine was 47.9% among healthcare workers when the WHO alert level was at phase 5. The most common reasons for an intention to accept were “wish to be protected” and “following health authority’s advice.” The major barriers identified were fear of side effects and doubts about efficacy. More than half of the respondents thought nurses should be the first priority group to receive the vaccines. The strongest positive associating factors were history of seasonal influenza vaccination and perceived risk of contracting the infection. Conclusions The willingness to accept pre-pandemic influenza vaccination was low, and no significant effect was observed with the change in WHO alert level. Further studies are required to elucidate the root cause of the low intention to accept pre-pandemic vaccination. In 2005 the World Health Organization recommended its member states to revise or construct a preparedness plan for pandemic influenza. The WHO also set up a system of influenza pandemic alert levels. Phases 1-3 include capacity development and response planning, while phases 4-6 signify the need for response and mitigation efforts. 1 By August 2008, 47 countries had prepared such a plan. 2 The recent spread of infection with a novel influenza A virus (H1N1 subtype) of swine origin ("swine flu") has prompted governments to review and carry out their pandemic responses, including vaccination strategies.