Question

why it is difficult to develop vaccines for some diseases​

Answer 1

Answer:

At a time when many infectious diseases were being brought or kept under control with global vaccination efforts in the 1990s, the human immunodeficiency virus (HIV), only identified in 1984, infected millions worldwide. From 1990 to 2014 the number of people living with HIV rose from 8 million to 36.9 million; since the beginning of the HIV/Acquired Immune Deficiency Syndrome (AIDS) epidemic, AIDS has claimed more than 34 million lives.[1]

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Answer 2

Answer:

HEY MATE

Explanation:

Vaccines are among the most ingenious of inventions, and among the most maddening.

Some global killers, like smallpox and polio, have been totally or nearly eradicated by products made with methods dating back to Louis Pasteur. Others, like malaria and H.I.V., utterly frustrate scientists to this day, despite astonishing new weapons like gene-editing.

We have a vaccine for Ebola that protects nearly 100 percent of its recipients, but we are lucky to get a routine flu shot that works half that well.

We have children’s vaccines against measles, mumps, rubella, diphtheria, whooping cough, tetanus, chickenpox, polio, hepatitis A and B, rotavirus, pneumococcus, haemophilus influenzae and meningococcal disease.

They have changed our expectations of mortality — and of parenthood. In 17th century England, one-third of all children died before age 15. Today, thanks largely to those vaccines, less than 1 percent of English children do.

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