Ok, here's another study that doesn't look at vaccines specifically, but rather the background of the disease they prevent, and how our bodies respond to it. In this case, influenza.
The researchers followed a small community of people in New York over the course of a flu season, looking at their antibody levels. The tests they used were neutralization (mixing serum with virus sample and seeing if the serum neutralized the virus so it didn't make mice sick) and complement fixation, though of the two tests the former seemed more useful.
In the period before the flu season, teenagers had the highest titers in the neutralization test, which were lower at younger and older ages. For complement fixation, the highest levels were in those 40 to 60 years old. Both tests observed a decrease above 60, in the elderly.
Then in the flu season, they made sure to distinguish clinical flu from the common cold or other flu-like illnesses: the flu was defined by a fever over 99 degrees F, headache, pains, general malaise, and respiratory symptoms. About 85% of the disease in the community was actually colds, which peaked in December, while the flu didn't peak until February. About 62% of the flu tested was found to be Influenza A, the rest other kinds.
So regarding the neutralization test results, having a cold didn't increase one's titers at all, but having the flu did (makes sense). Some had an increase without observing symptoms, possibly subclinical infections, too mild to be noticed. There was a definite correlation between having lower antibodies before the flu season and being likely to get the flu during the season, so titers correlated with protection. Though even those with the highest titers occasionally got sick.
One year after the season, some people's titers had returned to the same level they had been before the season (even if they got the flu), some stayed the same, the rest fell partway back. The average was 5 times more 1 year after than before.
So overall, it seems like higher titers correlate with more protection, but there's no really safe level that's 100% protective. And correlation isn't causation, so it's not clear the antibodies are doing the protecting, though neutralizing the virus seems like a good sign. Also I'm not sure how specific these tests are for specific antibodies, so they could show high levels of antibodies that aren't actually that useful, or something like that. Needs further study.
Reference:
The researchers followed a small community of people in New York over the course of a flu season, looking at their antibody levels. The tests they used were neutralization (mixing serum with virus sample and seeing if the serum neutralized the virus so it didn't make mice sick) and complement fixation, though of the two tests the former seemed more useful.
In the period before the flu season, teenagers had the highest titers in the neutralization test, which were lower at younger and older ages. For complement fixation, the highest levels were in those 40 to 60 years old. Both tests observed a decrease above 60, in the elderly.
Then in the flu season, they made sure to distinguish clinical flu from the common cold or other flu-like illnesses: the flu was defined by a fever over 99 degrees F, headache, pains, general malaise, and respiratory symptoms. About 85% of the disease in the community was actually colds, which peaked in December, while the flu didn't peak until February. About 62% of the flu tested was found to be Influenza A, the rest other kinds.
So regarding the neutralization test results, having a cold didn't increase one's titers at all, but having the flu did (makes sense). Some had an increase without observing symptoms, possibly subclinical infections, too mild to be noticed. There was a definite correlation between having lower antibodies before the flu season and being likely to get the flu during the season, so titers correlated with protection. Though even those with the highest titers occasionally got sick.
One year after the season, some people's titers had returned to the same level they had been before the season (even if they got the flu), some stayed the same, the rest fell partway back. The average was 5 times more 1 year after than before.
So overall, it seems like higher titers correlate with more protection, but there's no really safe level that's 100% protective. And correlation isn't causation, so it's not clear the antibodies are doing the protecting, though neutralizing the virus seems like a good sign. Also I'm not sure how specific these tests are for specific antibodies, so they could show high levels of antibodies that aren't actually that useful, or something like that. Needs further study.
Reference:
Rickard, E. R., Lennette, E. H. & Horsfall, F. L., Jr. A Comprehensive Study of Influenza in a Rural Community. Public Health Reports (1896-1970) 55, 2146–2167 (1940).
No comments:
Post a Comment