Influenza vaccines are produced in pathogen-free eggs that are 11 to 12 days old. The top of the egg is disinfected by wiping it with alcohol and then the egg is candled to identify a non-veinous area in the allantoic cavity where a small hole is poked to serve as a pressure release. A second hole is made at the top of the egg, where the influenza virus is injected in the allantoic cavity, past the chorioallantoic membrane. The two holes are then sealed with melted paraffin and the inoculated eggs are incubated for 48 hours at 37 degrees Celsius. During incubation time, the virus replicates and newly replicated viruses are released into the allantoic fluid