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Vaccine Safety
Vaccine "Hot Lots"
Question:
I've
heard there are "hot lots" of vaccines
that have been associated with more adverse
events and deaths than others and that parents
should find the numbers of these lots and not
allow their children to receive vaccines from
them.
Answer:
This
misconception got considerable publicity recently
when vaccine safety was the subject of a television
news program. First of all, the concept of
a "hot lot" of vaccine as it is used
in this context is wrong. It is based on the
presumption that the more reports to VAERS**
a vaccine lot is associated with, the more
dangerous the vaccine in that lot; and that
by consulting a list of the number of reports
per lot, a parent can identify vaccine lots
to avoid.
This is misleading for two reasons:
- VAERS is a system for reporting events that are temporally associated with
receipt of vaccine; VAERS reports should not be interpreted to imply causality. In other
words, a VAERS report does not mean that the vaccine caused the event. Statistically, a
certain number of serious illnesses, even deaths, can be expected to occur by chance alone
among children recently vaccinated. Although vaccines are known to cause minor, temporary
side effects such as soreness or fever, there is little, if any, evidence linking
vaccination with permanent health problems or death. The point is that just because an
adverse event has been reported to VAERS does not mean it was caused by a vaccine.
- Vaccine lots are not the same. The sizes of vaccine lots might vary from several
hundred thousand doses to several million, and some are in distribution much longer than
others. Naturally a larger lot or one that is in distribution longer will be associated
with more adverse events, simply by chance. Also, more coincidental deaths are associated
with vaccines given in infancy than later in childhood, since the background death rates
for children are highest during the first year of life. So knowing that lot A has been
associated with x number of adverse events while lot B has been associated with y number
would not necessarily say anything about the relative safety of the two lots, even if the
vaccine did cause the events.
Reviewing published lists of "hot lots" will not help parents identify the best
or worst vaccines for their children. If the number and type of VAERS reports for a
particular vaccine lot suggested that it was associated with more serious adverse events
or deaths than are expected by chance, the Food and Drug Administration (FDA) has the
legal authority to immediately recall that lot. To date, no vaccine lot in the modern era
has been found to be unsafe on the basis of VAERS reports.
All vaccine manufacturing facilities and vaccine products are licensed by the FDA. In
addition, every vaccine lot is safety-tested by the manufacturer. The results of these
tests are reviewed by FDA, who may repeat some of these tests as an additional protective
measure. FDA also inspects vaccine-manufacturing facilities regularly to ensure adherence
to manufacturing procedures and product-testing regulations, and reviews the weekly VAERS
reports for each lot searching for unusual patterns. FDA would recall a lot of vaccine at
the first sign of problems. There is no benefit to either the FDA or the manufacturer in
allowing unsafe vaccine to remain on the market. The American public would not tolerate
vaccines if they did not have to conform to the most rigorous safety standards. The mere
fact is that a vaccine lot still in distribution says that the FDA considers it safe.
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