or" href="#arguments"></a>Arguments</h2>
    <table class="ref-arguments">
    <colgroup><col class="name" /><col class="desc" /></colgroup>
    <tr>
      <th>region</th>
      <td><p>one of "<code>national</code>", "<code>hhs</code>", "<code>census</code>", or "<code>state</code>"</p></td>
    </tr>
    <tr>
      <th>years</th>
      <td><p>a vector of years to retrieve data for (i.e. <code>2014</code> for CDC
flu season 2014-2015). CDC has data for this API going back to 1997.
Default value (<code>NULL<