1.   A vaccine would require developing an immune response to a part of the virus that is relatively stable across all the variations.

2.   By delivering the drug this way, Aviron said it could eliminate the cost of syringes and medical waste disposal that vaccines require.

3.   For adults, the vaccine requires two injections.

4.   He said the new vaccine might require only two injections, instead of the six shots plus annual booster required with the current vaccine.

5.   Ideally, a new vaccine should require only two to three injections instead of the six shots plus annual booster given with the current vaccine, Strom said.

6.   The vaccine requires multiple shots over several years.

7.   Robinson said her vaccine requires only three shots and uses only three proteins.

8.   However, the vaccine requires booster shots to maintain its effectiveness and has side effects.

9.   In addition, this vaccine requires several booster shots to retain its effect and also has knock-on effects.