There's something strange about insisting that each person's life has "equal moral value", without bothering to assess how much each person stands to gain from continued life. One does not show equal concern towards two people by being indifferent to whether one receives a papercut or the other is beheaded. We should, of course, be indifferent to which of two people receives an equal benefit (else we would be treating the favoured person's interests as more important than the other person's). But it is no kind of favouritism to prefer that a greater benefit be bestowed upon whoever is able to receive it. Egalitarians are simply confused to suggest otherwise.
Harris claims that it is "ageist" to allocate medical resources efficiently, since it means we would sooner give a dose of life-saving antibiotics to a 20 year old (who can expect to gain 60+ years) than to a 90-year old with the same disease (who only expects to gain a couple of months from being cured of this particular ailment). I do not think that this should be considered "ageist". Again, we are not treating the elderly as less worthy of receiving an equal benefit. Rather, we are saying that, given a choice between offering a slight benefit to one person (who may be elderly), or else offering a much greater benefit to another person (who may be younger), the latter option is obviously preferable, on perfectly impartial grounds.
(Similar remarks apply to Harris' objections to the 'quality-adjusted' component of QALYs as being "discriminatory" towards those with a lower quality of life.)
Harris' central confusion is revealed in the following claim (p.121):
If for example some people were given life-saving treatment in preference to others because they had a better quality of life than those others... this would amount to regarding such people as more valuable than others on that account.
This simply isn't true. Again, we do not ordinarily think that equal moral concern for persons entails being indifferent between a smaller benefit for one or a larger benefit for another. Rather, we may regard people with equal concern (i.e. treat them as being equally "valuable" in themselves) by treating their welfare interests as mattering equally. And treating their interests equally should lead us to prefer that treatment go to whoever would benefit most from it.
Simply put: to say that someone would gain more from continued life is not to say that the person is more valuable than another. It is just to say that what the person gains is more valuable to that person than the alternative outcome is to the other person.
P.S. In principle, we need to assess possible harms and benefits in context: it's not as though a healthy year of life has constant value to all persons at all times. As I argue in 'Gambling Life for Immortality', the next forty years of healthy life are worth much more to me than a subsequent forty (even if they're equally healthy, etc.), in light of what I want to achieve during my lifetime. So the real problem with QALYs is that they are insufficiently discriminating! But of course practical policies cannot be so perfectly fine-tuned, so QALYs may be the best practicable guide to efficient resource allocation. They're certainly a vast improvement over Harris' proposed alternative.