Perhaps you should try some spelling variations:
"anti vaccine research : july 2009" » "anti medicine research : july 2009", "ant vaccine research : july 2009", "active vaccine research : july 2009", "aids vaccine research : july 2009", "anti vaccine research : july 2008", "anti vaccine research : july 2007", "anti vaccine research : july 2019"
"anti vaccine research : july 2012" » "anti medicine research : july 2012", "ant vaccine research : july 2012", "active vaccine research : july 2012", "aids vaccine research : july 2012", "anti vaccine research : july 2013"

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"anti vaccine research : july 2009\") OR (\"anti vaccine research : july 2012\"))~".
• Removing quotes may allow a broader search: (( anti vaccine research : july 2009 ) OR ( anti vaccine research : july 2012 ))~.
• Adding a wildcard symbol may retrieve word variants: (("anti vaccine research : july 2009") OR ("anti vaccine research : july 2012"))*.